A 45-year-old comes to the emergency department because of abdominal pain for the last few months. She has been belching and hiccuping, and she has lost 20 pounds.

A 45-year-old comes to the emergency department, where a CT scan shows a large mass in her stomach. There also are enlarged lymph nodes nearby and far away, and the wall of her abdomen is studded with smaller tumors.

A 45-year-old comes to the emergency department and is told she needs to be admitted to the hospital to work this up. It’s likely cancer, she is told, but the only way to confirm the diagnosis is with a biopsy. They do a procedure in which they insert a camera through her mouth and down her esophagus, and they take a sample of the large mass in her stomach. It is cancer – and it’s widely metastatic.

The resident on her team sends me a text. She wants to know: “What do you do in cases like this?”

Except she is not asking for my advice on medical management. The same day the patient is told it’s cancer, she has a confession. She has no insurance.

I read the text, then turn to the oncology case manager sitting next to me. We talk it through and the answer is as I suspected.

“She can be seen in the county clinic,” I text back, and give the name of an oncologist there. “Or, she can apply for emergency Medi-Cal to follow up at our hospital. But that process can take over a month to get approval.”

Except the case manager looks into it further. Actually, she does not qualify for emergency Medi-Cal because she invoked it earlier that year when she had an infection.

When it’s an emergency, hospitals tend to handle this kind of situation well. I’ve seen hospitals absorb the costs of major medical interventions when a person is acutely ill. They call it a charity case, and they cover all the costs of acute illness and treatment when the patient cannot.

But what this person needs is different. The treatment she needs is not emergent. What she needs is a regular oncologist who can give chemotherapy, monitor for side effects, check her blood counts, get regular scans to monitor the disease, and have conversations with her to navigate the bigger questions. What she needs is an ongoing relationship.

That is harder for a hospital to absorb.

I think back to a year ago, when I was volunteering at the free clinic. A 77-year-old man came in complaining of increased urinary frequency. I did a rectal exam, and I felt it: a large, irregular prostate mass. I thought of all I would normally do, down the algorithm of treatment – I’d order a PSA blood test, arrange for him to have a biopsy, likely get a CT scan, then get him back in the clinic to start treatment. But there, I could not do any of that. There, I was lucky when I could get someone a $4 medication. There, all I could do was hand him the truth. “I am concerned you have prostate cancer,” I said.

I remember how he began crying tears of joy. “God bless you,” he said, grabbing my hand. God bless me? For what? For handing him a problem but no solution? For sharing a suspicion of a diagnosis that could kill him but being unable to intervene? Is it really better knowing?

I deliver a lot of bad news in oncology, but I usually get to blame the disease. The cancer is aggressive. The cancer is causing your pain.

What I hate perhaps even more is the other type of bad news: having our hands tied by a system I disagree with – and yet am somehow part of. We can offer X, but not Y. You can be seen in this clinic, but not in that one. This treatment is covered, but that part would be out of pocket. Negotiating what is absolutely necessary and what is preferred.

A 45-year-old comes to the emergency department with abdominal pain. She is told she has metastatic cancer that will take her life in less than 6 months without treatment. She has many questions for me, the inpatient oncology fellow. But they are not about the disease, the prognosis, or the treatment. They are all about insurance options, reimbursement, and cost.

Like everyone with a new devastating diagnosis, she is weighing her options. Except her decisions are weighted with the fear of bankruptcy; her calculus trying to compute the cost of her life.

“I wish things were different,” I say.

Minor details of this story were altered to protect privacy.

Dr. Yurkiewicz is a fellow in hematology and oncology at Stanford (Calif.) University. Follow her on Twitter @ilanayurkiewicz.

 

A 45-year-old comes to the emergency department because of abdominal pain for the last few months. She has been belching and hiccuping, and she has lost 20 pounds.

A 45-year-old comes to the emergency department, where a CT scan shows a large mass in her stomach. There also are enlarged lymph nodes nearby and far away, and the wall of her abdomen is studded with smaller tumors.

A 45-year-old comes to the emergency department and is told she needs to be admitted to the hospital to work this up. It’s likely cancer, she is told, but the only way to confirm the diagnosis is with a biopsy. They do a procedure in which they insert a camera through her mouth and down her esophagus, and they take a sample of the large mass in her stomach. It is cancer – and it’s widely metastatic.

The resident on her team sends me a text. She wants to know: “What do you do in cases like this?”

Except she is not asking for my advice on medical management. The same day the patient is told it’s cancer, she has a confession. She has no insurance.

I read the text, then turn to the oncology case manager sitting next to me. We talk it through and the answer is as I suspected.

“She can be seen in the county clinic,” I text back, and give the name of an oncologist there. “Or, she can apply for emergency Medi-Cal to follow up at our hospital. But that process can take over a month to get approval.”

Except the case manager looks into it further. Actually, she does not qualify for emergency Medi-Cal because she invoked it earlier that year when she had an infection.

When it’s an emergency, hospitals tend to handle this kind of situation well. I’ve seen hospitals absorb the costs of major medical interventions when a person is acutely ill. They call it a charity case, and they cover all the costs of acute illness and treatment when the patient cannot.

But what this person needs is different. The treatment she needs is not emergent. What she needs is a regular oncologist who can give chemotherapy, monitor for side effects, check her blood counts, get regular scans to monitor the disease, and have conversations with her to navigate the bigger questions. What she needs is an ongoing relationship.

That is harder for a hospital to absorb.

I think back to a year ago, when I was volunteering at the free clinic. A 77-year-old man came in complaining of increased urinary frequency. I did a rectal exam, and I felt it: a large, irregular prostate mass. I thought of all I would normally do, down the algorithm of treatment – I’d order a PSA blood test, arrange for him to have a biopsy, likely get a CT scan, then get him back in the clinic to start treatment. But there, I could not do any of that. There, I was lucky when I could get someone a $4 medication. There, all I could do was hand him the truth. “I am concerned you have prostate cancer,” I said.

I remember how he began crying tears of joy. “God bless you,” he said, grabbing my hand. God bless me? For what? For handing him a problem but no solution? For sharing a suspicion of a diagnosis that could kill him but being unable to intervene? Is it really better knowing?

I deliver a lot of bad news in oncology, but I usually get to blame the disease. The cancer is aggressive. The cancer is causing your pain.

What I hate perhaps even more is the other type of bad news: having our hands tied by a system I disagree with – and yet am somehow part of. We can offer X, but not Y. You can be seen in this clinic, but not in that one. This treatment is covered, but that part would be out of pocket. Negotiating what is absolutely necessary and what is preferred.

A 45-year-old comes to the emergency department with abdominal pain. She is told she has metastatic cancer that will take her life in less than 6 months without treatment. She has many questions for me, the inpatient oncology fellow. But they are not about the disease, the prognosis, or the treatment. They are all about insurance options, reimbursement, and cost.

Like everyone with a new devastating diagnosis, she is weighing her options. Except her decisions are weighted with the fear of bankruptcy; her calculus trying to compute the cost of her life.

“I wish things were different,” I say.

Minor details of this story were altered to protect privacy.

Dr. Yurkiewicz is a fellow in hematology and oncology at Stanford (Calif.) University. Follow her on Twitter @ilanayurkiewicz.

 

A 45-year-old comes to the emergency department because of abdominal pain for the last few months. She has been belching and hiccuping, and she has lost 20 pounds.

A 45-year-old comes to the emergency department, where a CT scan shows a large mass in her stomach. There also are enlarged lymph nodes nearby and far away, and the wall of her abdomen is studded with smaller tumors.

A 45-year-old comes to the emergency department and is told she needs to be admitted to the hospital to work this up. It’s likely cancer, she is told, but the only way to confirm the diagnosis is with a biopsy. They do a procedure in which they insert a camera through her mouth and down her esophagus, and they take a sample of the large mass in her stomach. It is cancer – and it’s widely metastatic.

The resident on her team sends me a text. She wants to know: “What do you do in cases like this?”

Except she is not asking for my advice on medical management. The same day the patient is told it’s cancer, she has a confession. She has no insurance.

I read the text, then turn to the oncology case manager sitting next to me. We talk it through and the answer is as I suspected.

“She can be seen in the county clinic,” I text back, and give the name of an oncologist there. “Or, she can apply for emergency Medi-Cal to follow up at our hospital. But that process can take over a month to get approval.”

Except the case manager looks into it further. Actually, she does not qualify for emergency Medi-Cal because she invoked it earlier that year when she had an infection.

When it’s an emergency, hospitals tend to handle this kind of situation well. I’ve seen hospitals absorb the costs of major medical interventions when a person is acutely ill. They call it a charity case, and they cover all the costs of acute illness and treatment when the patient cannot.

But what this person needs is different. The treatment she needs is not emergent. What she needs is a regular oncologist who can give chemotherapy, monitor for side effects, check her blood counts, get regular scans to monitor the disease, and have conversations with her to navigate the bigger questions. What she needs is an ongoing relationship.

That is harder for a hospital to absorb.

I think back to a year ago, when I was volunteering at the free clinic. A 77-year-old man came in complaining of increased urinary frequency. I did a rectal exam, and I felt it: a large, irregular prostate mass. I thought of all I would normally do, down the algorithm of treatment – I’d order a PSA blood test, arrange for him to have a biopsy, likely get a CT scan, then get him back in the clinic to start treatment. But there, I could not do any of that. There, I was lucky when I could get someone a $4 medication. There, all I could do was hand him the truth. “I am concerned you have prostate cancer,” I said.

I remember how he began crying tears of joy. “God bless you,” he said, grabbing my hand. God bless me? For what? For handing him a problem but no solution? For sharing a suspicion of a diagnosis that could kill him but being unable to intervene? Is it really better knowing?

I deliver a lot of bad news in oncology, but I usually get to blame the disease. The cancer is aggressive. The cancer is causing your pain.

What I hate perhaps even more is the other type of bad news: having our hands tied by a system I disagree with – and yet am somehow part of. We can offer X, but not Y. You can be seen in this clinic, but not in that one. This treatment is covered, but that part would be out of pocket. Negotiating what is absolutely necessary and what is preferred.

A 45-year-old comes to the emergency department with abdominal pain. She is told she has metastatic cancer that will take her life in less than 6 months without treatment. She has many questions for me, the inpatient oncology fellow. But they are not about the disease, the prognosis, or the treatment. They are all about insurance options, reimbursement, and cost.

Like everyone with a new devastating diagnosis, she is weighing her options. Except her decisions are weighted with the fear of bankruptcy; her calculus trying to compute the cost of her life.

“I wish things were different,” I say.

Minor details of this story were altered to protect privacy.

Dr. Yurkiewicz is a fellow in hematology and oncology at Stanford (Calif.) University. Follow her on Twitter @ilanayurkiewicz.

 

Recall that melatonin displays multiple biological functions, acting as an antioxidant, cytokine, neurotransmitter, and global regulator of the circadian clock, the latter for which it is best known.^1-3 At the cutaneous level, melatonin exhibits antioxidant (direct, as a radical scavenger; indirect, through upregulating antioxidant enzymes), anti-inflammatory, photoprotective, tissue regenerative, and cytoprotective activity, particularly in its capacity to preserve mitochondrial function.^4-8

Melatonin also protects skin homeostasis,⁶ and, consequently, is believed to act against carcinogenesis and potentially other deleterious dysfunctions such as hyperproliferative/inflammatory conditions.⁵ Notably, functional melatonin receptors are expressed in human skin and hair follicles, where melatonin is also produced, further buttressing the critical role that melatonin plays in skin health.⁵ Melatonin also displays immunomodulatory, thermoregulatory, and antitumor functions.⁹ The topical application of melatonin has been demonstrated to diminish markers of reactive oxygen species as well as reverse manifestations of cutaneous aging.⁵

Melatonin is both produced by and metabolized in the skin. The hormone and its metabolites (6-hydroxymelatonin, N¹-acetyl-N²-formyl-5-methoxykynuramine [AFMK], N-acetyl-serotonin, and 5-methoxytryptamine) reduce UVB-induced oxidative cell damage in human keratinocytes and melanocytes, and also act as radioprotectors.⁶

Melatonin has been shown to protect human dermal fibroblasts from UVA- and UVB-induced damage.⁹ In addition, melatonin and its metabolites have been demonstrated to suppress the growth of cultured human melanomas, and high doses of melatonin used in clinical trials in late metastatic melanoma stages have enhanced the efficacy of or diminished the side effects of chemotherapy/chemo-immunotherapy.⁹

UVB and melatonin in the lab

In a 2018 hairless mouse study in which animals were irradiated by UVB for 8 weeks, Park et al. showed that melatonin displays anti-wrinkle activity by suppressing reactive oxygen species- and sonic hedgehog-mediated inflammatory proteins. Melatonin also protected against transepidermal water loss and prevented epidermal thickness as well as dermal collagen degradation.¹⁰

Also that year, Skobowiat et al. found that the topical application of melatonin and its active derivatives (N1-acetyl-N2-formyl-5-methoxykynurenine and N-acetylserotonin) yielded photoprotective effects pre- and post-UVB treatment in human and porcine skin ex vivo. They concluded that their results justify additional investigation of the clinical applications of melatonin and its metabolites for its potential to exert protective effects against UVB in human subjects.⁸

Although the preponderance of previous work identifies melatonin as a strong antioxidant, Kocyigit et al. reported in 2018 on new in vitro studies suggesting that melatonin dose-dependently exerts cytotoxic and apoptotic activity on several cell types, including both human epidermoid carcinoma and normal skin fibroblasts. Their findings showed that melatonin exhibited proliferative effects on cancerous and normal cells at low doses and cytotoxic effects at high doses.¹¹
 

Melatonin as a sunscreen ingredient

Further supporting its use in the topical armamentarium for skin health, melatonin is a key ingredient in a sunscreen formulation, the creation of which was driven by the need to protect the skin of military personnel facing lengthy UV exposure. Specifically, the formulation containing avobenzone, octinoxate, oxybenzone, and titanium dioxide along with melatonin and pumpkin seed oil underwent a preclinical safety evaluation in 2017, as reported by Bora et al. The formulation was found to be nonmutagenic, nontoxic, and safe in animal models and is deemed ready to test for its efficacy in humans.¹² Melatonin is also among a host of systemic treatment options for skin lightening.¹³

 

Oral and topical melatonin in human studies

In a 2017 study on the impact of melatonin treatment on the skin of former smokers, Sagan et al. assessed oxidative damage to membrane lipids in blood serum and in epidermis exfoliated during microdermabrasion (at baseline, 2 weeks after, and 4 weeks after treatment) in postmenopausal women. Never smokers (n = 44) and former smokers (n = 46) were divided into control, melatonin topical, antioxidant topical, and melatonin oral treatment groups. The investigators found that after only 2 weeks, melatonin oral treatment significantly reversed the elevated serum lipid peroxidation in former smokers. Oral melatonin increased elasticity, moisture, and sebum levels after 4 weeks of treatment and topical melatonin increased sebum level. They concluded that the use of exogenous melatonin reverses the effects of oxidative damage to membrane lipids and ameliorates cutaneous biophysical traits in postmenopausal women who once smoked. The researchers added that melatonin use for all former smokers is warranted and that topically applied melatonin merits consideration for improving the effects of facial microdermabrasion.¹⁴

In a systematic literature review in 2017, Scheuer identified 20 studies (4 human and 16 experimental) indicating that melatonin exerts a protective effect against artificial UV-induced erythema when applied pre-exposure.⁷ Also that year, Scheuer and colleagues conducted randomized, double-blind, placebo-controlled work demonstrating that topical melatonin (12.5%) significantly reduced erythema resulting from natural sunlight, and in a separate randomized, double-blind, placebo-controlled crossover study that the same concentration of a full body application of melatonin exhibited no significant impact on cognition and should be considered safe for dermal application.⁷ Scheuer added that additional longitudinal research is needed to ascertain effects of topical melatonin usage over time.

Early in 2018, Milani and Sparavigna reported on a randomized, split-face, assessor-blinded, prospective 3-month study of 22 women (mean age 55 years) with moderate to severe facial skin aging; the study was designed to test the efficacy of melatonin-based day and night creams. All of the women completed the proof-of-concept trial in which crow’s feet were found to be significantly diminished on the sides of the face treated with the creams compared with the nontreated skin.

Image Source/getty images

Both well-tolerated melatonin formulations were associated with significant improvements in surface microrelief, skin profilometry, tonicity, and dryness. With marked enhancement of skin hydration and reduction of roughness noted, the investigators concluded that their results supported the notion that the tested melatonin topical formulations yielded antiaging effects.⁴

Conclusion

The majority of research on the potent hormone melatonin over nearly the last quarter century indicates that this dynamic substance provides multifaceted benefits in performing several biological functions. Topical melatonin is available over the counter. Its expanded use in skin care warrants greater attention as we learn more about this versatile endogenous substance.

Dr. Baumann is a private practice dermatologist, researcher, author, and entrepreneur who practices in Miami. She founded the Cosmetic Dermatology Center at the University of Miami in 1997. Dr. Baumann wrote two textbooks: “Cosmetic Dermatology: Principles and Practice” (New York: McGraw-Hill, 2002), and “Cosmeceuticals and Cosmetic Ingredients,” (New York: McGraw-Hill, 2014), and a New York Times Best Sellers book for consumers, “The Skin Type Solution” (New York: Bantam Dell, 2006). Dr. Baumann has received funding for advisory boards and/or clinical research trials from Allergan, Evolus, Galderma, and Revance. She is the founder and CEO of Skin Type Solutions Franchise Systems LLC. Write to her at [email protected].

 

References

1. Zmijewski MA et al. Dermatoendocrinol. 2011 Jan;3(1):3-10.

2. Slominski A et al. Trends Endocrinol Metab. 2008 Jan;19(1):17-24.

3. Slominski A et al. J Cell Physiol. 2003 Jul;196(1):144-53.

4. Milani M et al. Clin Cosmet Investig Dermatol. 2018 Jan 24;11:51-7.

5. Day D et al. J Drugs Dermatol. 2018 Sep 1;17(9):966-9.

6. Slominski AT et al. Cell Mol Life Sci. 2017 Nov;74(21):3913-25.

7. Scheuer C. Dan Med J. 2017 Jun;64(6). pii:B5358.

8. Skobowiat C et al. J Pineal Res. 2018 Sep;65(2):e12501.

9. Slominski AT et al. J Invest Dermatol. 2018 Mar;138(3):490-9.

10. Park EK et al. Int J Mol Sci. 2018 Jul 8;19(7). pii: E1995.

11. Kocyigit A et al. Mutat Res. 2018 May-Jun;829-30:50-60.

12. Bora NS et al. Regul Toxicol Pharmacol. 2017 Oct;89:1-12.

13. Juhasz MLW et al. J Cosmet Dermatol. 2018 Dec;17(6):1144-57.

14. Sagan D et al. Ann Agric Environ Med. 2017 Dec 23;24(4):659-66.

 

Recall that melatonin displays multiple biological functions, acting as an antioxidant, cytokine, neurotransmitter, and global regulator of the circadian clock, the latter for which it is best known.^1-3 At the cutaneous level, melatonin exhibits antioxidant (direct, as a radical scavenger; indirect, through upregulating antioxidant enzymes), anti-inflammatory, photoprotective, tissue regenerative, and cytoprotective activity, particularly in its capacity to preserve mitochondrial function.^4-8

Melatonin also protects skin homeostasis,⁶ and, consequently, is believed to act against carcinogenesis and potentially other deleterious dysfunctions such as hyperproliferative/inflammatory conditions.⁵ Notably, functional melatonin receptors are expressed in human skin and hair follicles, where melatonin is also produced, further buttressing the critical role that melatonin plays in skin health.⁵ Melatonin also displays immunomodulatory, thermoregulatory, and antitumor functions.⁹ The topical application of melatonin has been demonstrated to diminish markers of reactive oxygen species as well as reverse manifestations of cutaneous aging.⁵

Melatonin is both produced by and metabolized in the skin. The hormone and its metabolites (6-hydroxymelatonin, N¹-acetyl-N²-formyl-5-methoxykynuramine [AFMK], N-acetyl-serotonin, and 5-methoxytryptamine) reduce UVB-induced oxidative cell damage in human keratinocytes and melanocytes, and also act as radioprotectors.⁶

Melatonin has been shown to protect human dermal fibroblasts from UVA- and UVB-induced damage.⁹ In addition, melatonin and its metabolites have been demonstrated to suppress the growth of cultured human melanomas, and high doses of melatonin used in clinical trials in late metastatic melanoma stages have enhanced the efficacy of or diminished the side effects of chemotherapy/chemo-immunotherapy.⁹

UVB and melatonin in the lab

In a 2018 hairless mouse study in which animals were irradiated by UVB for 8 weeks, Park et al. showed that melatonin displays anti-wrinkle activity by suppressing reactive oxygen species- and sonic hedgehog-mediated inflammatory proteins. Melatonin also protected against transepidermal water loss and prevented epidermal thickness as well as dermal collagen degradation.¹⁰

Also that year, Skobowiat et al. found that the topical application of melatonin and its active derivatives (N1-acetyl-N2-formyl-5-methoxykynurenine and N-acetylserotonin) yielded photoprotective effects pre- and post-UVB treatment in human and porcine skin ex vivo. They concluded that their results justify additional investigation of the clinical applications of melatonin and its metabolites for its potential to exert protective effects against UVB in human subjects.⁸

Although the preponderance of previous work identifies melatonin as a strong antioxidant, Kocyigit et al. reported in 2018 on new in vitro studies suggesting that melatonin dose-dependently exerts cytotoxic and apoptotic activity on several cell types, including both human epidermoid carcinoma and normal skin fibroblasts. Their findings showed that melatonin exhibited proliferative effects on cancerous and normal cells at low doses and cytotoxic effects at high doses.¹¹
 

Melatonin as a sunscreen ingredient

Further supporting its use in the topical armamentarium for skin health, melatonin is a key ingredient in a sunscreen formulation, the creation of which was driven by the need to protect the skin of military personnel facing lengthy UV exposure. Specifically, the formulation containing avobenzone, octinoxate, oxybenzone, and titanium dioxide along with melatonin and pumpkin seed oil underwent a preclinical safety evaluation in 2017, as reported by Bora et al. The formulation was found to be nonmutagenic, nontoxic, and safe in animal models and is deemed ready to test for its efficacy in humans.¹² Melatonin is also among a host of systemic treatment options for skin lightening.¹³

 

Oral and topical melatonin in human studies

In a 2017 study on the impact of melatonin treatment on the skin of former smokers, Sagan et al. assessed oxidative damage to membrane lipids in blood serum and in epidermis exfoliated during microdermabrasion (at baseline, 2 weeks after, and 4 weeks after treatment) in postmenopausal women. Never smokers (n = 44) and former smokers (n = 46) were divided into control, melatonin topical, antioxidant topical, and melatonin oral treatment groups. The investigators found that after only 2 weeks, melatonin oral treatment significantly reversed the elevated serum lipid peroxidation in former smokers. Oral melatonin increased elasticity, moisture, and sebum levels after 4 weeks of treatment and topical melatonin increased sebum level. They concluded that the use of exogenous melatonin reverses the effects of oxidative damage to membrane lipids and ameliorates cutaneous biophysical traits in postmenopausal women who once smoked. The researchers added that melatonin use for all former smokers is warranted and that topically applied melatonin merits consideration for improving the effects of facial microdermabrasion.¹⁴

In a systematic literature review in 2017, Scheuer identified 20 studies (4 human and 16 experimental) indicating that melatonin exerts a protective effect against artificial UV-induced erythema when applied pre-exposure.⁷ Also that year, Scheuer and colleagues conducted randomized, double-blind, placebo-controlled work demonstrating that topical melatonin (12.5%) significantly reduced erythema resulting from natural sunlight, and in a separate randomized, double-blind, placebo-controlled crossover study that the same concentration of a full body application of melatonin exhibited no significant impact on cognition and should be considered safe for dermal application.⁷ Scheuer added that additional longitudinal research is needed to ascertain effects of topical melatonin usage over time.

Early in 2018, Milani and Sparavigna reported on a randomized, split-face, assessor-blinded, prospective 3-month study of 22 women (mean age 55 years) with moderate to severe facial skin aging; the study was designed to test the efficacy of melatonin-based day and night creams. All of the women completed the proof-of-concept trial in which crow’s feet were found to be significantly diminished on the sides of the face treated with the creams compared with the nontreated skin.

Image Source/getty images

Both well-tolerated melatonin formulations were associated with significant improvements in surface microrelief, skin profilometry, tonicity, and dryness. With marked enhancement of skin hydration and reduction of roughness noted, the investigators concluded that their results supported the notion that the tested melatonin topical formulations yielded antiaging effects.⁴

Conclusion

The majority of research on the potent hormone melatonin over nearly the last quarter century indicates that this dynamic substance provides multifaceted benefits in performing several biological functions. Topical melatonin is available over the counter. Its expanded use in skin care warrants greater attention as we learn more about this versatile endogenous substance.

Dr. Baumann is a private practice dermatologist, researcher, author, and entrepreneur who practices in Miami. She founded the Cosmetic Dermatology Center at the University of Miami in 1997. Dr. Baumann wrote two textbooks: “Cosmetic Dermatology: Principles and Practice” (New York: McGraw-Hill, 2002), and “Cosmeceuticals and Cosmetic Ingredients,” (New York: McGraw-Hill, 2014), and a New York Times Best Sellers book for consumers, “The Skin Type Solution” (New York: Bantam Dell, 2006). Dr. Baumann has received funding for advisory boards and/or clinical research trials from Allergan, Evolus, Galderma, and Revance. She is the founder and CEO of Skin Type Solutions Franchise Systems LLC. Write to her at [email protected].

 

References

1. Zmijewski MA et al. Dermatoendocrinol. 2011 Jan;3(1):3-10.

2. Slominski A et al. Trends Endocrinol Metab. 2008 Jan;19(1):17-24.

3. Slominski A et al. J Cell Physiol. 2003 Jul;196(1):144-53.

4. Milani M et al. Clin Cosmet Investig Dermatol. 2018 Jan 24;11:51-7.

5. Day D et al. J Drugs Dermatol. 2018 Sep 1;17(9):966-9.

6. Slominski AT et al. Cell Mol Life Sci. 2017 Nov;74(21):3913-25.

7. Scheuer C. Dan Med J. 2017 Jun;64(6). pii:B5358.

8. Skobowiat C et al. J Pineal Res. 2018 Sep;65(2):e12501.

9. Slominski AT et al. J Invest Dermatol. 2018 Mar;138(3):490-9.

10. Park EK et al. Int J Mol Sci. 2018 Jul 8;19(7). pii: E1995.

11. Kocyigit A et al. Mutat Res. 2018 May-Jun;829-30:50-60.

12. Bora NS et al. Regul Toxicol Pharmacol. 2017 Oct;89:1-12.

13. Juhasz MLW et al. J Cosmet Dermatol. 2018 Dec;17(6):1144-57.

14. Sagan D et al. Ann Agric Environ Med. 2017 Dec 23;24(4):659-66.

 

Recall that melatonin displays multiple biological functions, acting as an antioxidant, cytokine, neurotransmitter, and global regulator of the circadian clock, the latter for which it is best known.^1-3 At the cutaneous level, melatonin exhibits antioxidant (direct, as a radical scavenger; indirect, through upregulating antioxidant enzymes), anti-inflammatory, photoprotective, tissue regenerative, and cytoprotective activity, particularly in its capacity to preserve mitochondrial function.^4-8

Melatonin also protects skin homeostasis,⁶ and, consequently, is believed to act against carcinogenesis and potentially other deleterious dysfunctions such as hyperproliferative/inflammatory conditions.⁵ Notably, functional melatonin receptors are expressed in human skin and hair follicles, where melatonin is also produced, further buttressing the critical role that melatonin plays in skin health.⁵ Melatonin also displays immunomodulatory, thermoregulatory, and antitumor functions.⁹ The topical application of melatonin has been demonstrated to diminish markers of reactive oxygen species as well as reverse manifestations of cutaneous aging.⁵

Melatonin is both produced by and metabolized in the skin. The hormone and its metabolites (6-hydroxymelatonin, N¹-acetyl-N²-formyl-5-methoxykynuramine [AFMK], N-acetyl-serotonin, and 5-methoxytryptamine) reduce UVB-induced oxidative cell damage in human keratinocytes and melanocytes, and also act as radioprotectors.⁶

Melatonin has been shown to protect human dermal fibroblasts from UVA- and UVB-induced damage.⁹ In addition, melatonin and its metabolites have been demonstrated to suppress the growth of cultured human melanomas, and high doses of melatonin used in clinical trials in late metastatic melanoma stages have enhanced the efficacy of or diminished the side effects of chemotherapy/chemo-immunotherapy.⁹

UVB and melatonin in the lab

In a 2018 hairless mouse study in which animals were irradiated by UVB for 8 weeks, Park et al. showed that melatonin displays anti-wrinkle activity by suppressing reactive oxygen species- and sonic hedgehog-mediated inflammatory proteins. Melatonin also protected against transepidermal water loss and prevented epidermal thickness as well as dermal collagen degradation.¹⁰

Also that year, Skobowiat et al. found that the topical application of melatonin and its active derivatives (N1-acetyl-N2-formyl-5-methoxykynurenine and N-acetylserotonin) yielded photoprotective effects pre- and post-UVB treatment in human and porcine skin ex vivo. They concluded that their results justify additional investigation of the clinical applications of melatonin and its metabolites for its potential to exert protective effects against UVB in human subjects.⁸

Although the preponderance of previous work identifies melatonin as a strong antioxidant, Kocyigit et al. reported in 2018 on new in vitro studies suggesting that melatonin dose-dependently exerts cytotoxic and apoptotic activity on several cell types, including both human epidermoid carcinoma and normal skin fibroblasts. Their findings showed that melatonin exhibited proliferative effects on cancerous and normal cells at low doses and cytotoxic effects at high doses.¹¹
 

Melatonin as a sunscreen ingredient

Further supporting its use in the topical armamentarium for skin health, melatonin is a key ingredient in a sunscreen formulation, the creation of which was driven by the need to protect the skin of military personnel facing lengthy UV exposure. Specifically, the formulation containing avobenzone, octinoxate, oxybenzone, and titanium dioxide along with melatonin and pumpkin seed oil underwent a preclinical safety evaluation in 2017, as reported by Bora et al. The formulation was found to be nonmutagenic, nontoxic, and safe in animal models and is deemed ready to test for its efficacy in humans.¹² Melatonin is also among a host of systemic treatment options for skin lightening.¹³

 

Oral and topical melatonin in human studies

In a 2017 study on the impact of melatonin treatment on the skin of former smokers, Sagan et al. assessed oxidative damage to membrane lipids in blood serum and in epidermis exfoliated during microdermabrasion (at baseline, 2 weeks after, and 4 weeks after treatment) in postmenopausal women. Never smokers (n = 44) and former smokers (n = 46) were divided into control, melatonin topical, antioxidant topical, and melatonin oral treatment groups. The investigators found that after only 2 weeks, melatonin oral treatment significantly reversed the elevated serum lipid peroxidation in former smokers. Oral melatonin increased elasticity, moisture, and sebum levels after 4 weeks of treatment and topical melatonin increased sebum level. They concluded that the use of exogenous melatonin reverses the effects of oxidative damage to membrane lipids and ameliorates cutaneous biophysical traits in postmenopausal women who once smoked. The researchers added that melatonin use for all former smokers is warranted and that topically applied melatonin merits consideration for improving the effects of facial microdermabrasion.¹⁴

In a systematic literature review in 2017, Scheuer identified 20 studies (4 human and 16 experimental) indicating that melatonin exerts a protective effect against artificial UV-induced erythema when applied pre-exposure.⁷ Also that year, Scheuer and colleagues conducted randomized, double-blind, placebo-controlled work demonstrating that topical melatonin (12.5%) significantly reduced erythema resulting from natural sunlight, and in a separate randomized, double-blind, placebo-controlled crossover study that the same concentration of a full body application of melatonin exhibited no significant impact on cognition and should be considered safe for dermal application.⁷ Scheuer added that additional longitudinal research is needed to ascertain effects of topical melatonin usage over time.

Early in 2018, Milani and Sparavigna reported on a randomized, split-face, assessor-blinded, prospective 3-month study of 22 women (mean age 55 years) with moderate to severe facial skin aging; the study was designed to test the efficacy of melatonin-based day and night creams. All of the women completed the proof-of-concept trial in which crow’s feet were found to be significantly diminished on the sides of the face treated with the creams compared with the nontreated skin.

Image Source/getty images

Both well-tolerated melatonin formulations were associated with significant improvements in surface microrelief, skin profilometry, tonicity, and dryness. With marked enhancement of skin hydration and reduction of roughness noted, the investigators concluded that their results supported the notion that the tested melatonin topical formulations yielded antiaging effects.⁴

Conclusion

The majority of research on the potent hormone melatonin over nearly the last quarter century indicates that this dynamic substance provides multifaceted benefits in performing several biological functions. Topical melatonin is available over the counter. Its expanded use in skin care warrants greater attention as we learn more about this versatile endogenous substance.

Dr. Baumann is a private practice dermatologist, researcher, author, and entrepreneur who practices in Miami. She founded the Cosmetic Dermatology Center at the University of Miami in 1997. Dr. Baumann wrote two textbooks: “Cosmetic Dermatology: Principles and Practice” (New York: McGraw-Hill, 2002), and “Cosmeceuticals and Cosmetic Ingredients,” (New York: McGraw-Hill, 2014), and a New York Times Best Sellers book for consumers, “The Skin Type Solution” (New York: Bantam Dell, 2006). Dr. Baumann has received funding for advisory boards and/or clinical research trials from Allergan, Evolus, Galderma, and Revance. She is the founder and CEO of Skin Type Solutions Franchise Systems LLC. Write to her at [email protected].

 

References

1. Zmijewski MA et al. Dermatoendocrinol. 2011 Jan;3(1):3-10.

2. Slominski A et al. Trends Endocrinol Metab. 2008 Jan;19(1):17-24.

3. Slominski A et al. J Cell Physiol. 2003 Jul;196(1):144-53.

4. Milani M et al. Clin Cosmet Investig Dermatol. 2018 Jan 24;11:51-7.

5. Day D et al. J Drugs Dermatol. 2018 Sep 1;17(9):966-9.

6. Slominski AT et al. Cell Mol Life Sci. 2017 Nov;74(21):3913-25.

7. Scheuer C. Dan Med J. 2017 Jun;64(6). pii:B5358.

8. Skobowiat C et al. J Pineal Res. 2018 Sep;65(2):e12501.

9. Slominski AT et al. J Invest Dermatol. 2018 Mar;138(3):490-9.

10. Park EK et al. Int J Mol Sci. 2018 Jul 8;19(7). pii: E1995.

11. Kocyigit A et al. Mutat Res. 2018 May-Jun;829-30:50-60.

12. Bora NS et al. Regul Toxicol Pharmacol. 2017 Oct;89:1-12.

13. Juhasz MLW et al. J Cosmet Dermatol. 2018 Dec;17(6):1144-57.

14. Sagan D et al. Ann Agric Environ Med. 2017 Dec 23;24(4):659-66.

The complete blood cell count (CBC) is one of the most frequently ordered laboratory tests in both the inpatient and outpatient settings. Not long ago, the CBC required peering through a microscope and counting the red blood cells, white blood cells, and platelets. These 3 numbers are still the primary purpose of the test.

Now, with automated counters, the CBC report also contains other numbers that delineate characteristics of each cell type. For example:

The mean corpuscular volume is the average volume of red blood cells. Providers use it to classify anemia as either microcytic, normocytic, or macrocytic, each with its own differential diagnosis.

The differential white blood cell count provides absolute counts and relative percentages of each type of leukocyte. For example, the absolute neutrophil count is an important measure of immunocompetence.

But other values in the CBC may be overlooked, even though they can provide important information. Here, we highlight 3 of them:

• The red blood cell distribution width (RDW)
• The mean platelet volume (MPV)
• The nucleated red blood cell (NRBC) count.

In addition to describing their diagnostic utility, we also discuss emerging evidence of their potential prognostic significance in hematologic and nonhematologic disorders. By incorporating an awareness of their value in clinical practice, providers can maximize the usefulness of the CBC.

RED BLOOD CELL DISTRIBUTION WIDTH

The RDW is a measure of variation (anisocytosis) in the size of the circulating red cells. The term “width” is misleading, as the value is not derived from the width of the red blood cell, but rather from the width of the distribution curve of the corpuscular volume (Figure 1). Therefore, a normal RDW means that the cells are all about the same size, while a high RDW means they vary widely in size.

The RDW can be calculated either as a coefficient of variation, with a reference range of 11% to 16% depending on the laboratory, or, less often, as a standard deviation, with a reference range of 39 to 46 fL.

The RDW can differentiate between causes of anemia

A high RDW is often found in nutritional deficiencies of iron, vitamin B₁₂, and folate. This information is helpful in differentiating the cause of microcytic anemia, as a high RDW suggests iron-deficiency anemia while a normal RDW suggests thalassemia.¹ In iron deficiency, the RDW often rises before the mean corpuscular volume falls, serving as an early diagnostic clue.

The RDW can also be high after recent hemorrhage or rapid hemolysis, as the acute drop in hemoglobin results in increased production of reticulocytes, which are larger than mature erythrocytes.

Because a range of disorders can elevate the RDW, reviewing the peripheral blood smear is an important next step in the diagnostic evaluation, specifically looking for reticulocytes, microspherocytes, and other abnormal red blood cells contributing to the RDW elevation.

A normal RDW is less diagnostically useful. It indicates the red blood cells are of uniform size, but they may be uniformly small or large depending on how long the anemia has persisted. Since red cells circulate for only about 120 days, patients who have severe iron-deficiency anemia for months to years are expected to have a normal rather than a high RDW, as their red cells of normal size have all been replaced by microcytes.

A low RDW is not consistently associated with any hematologic disorder.

RDW may have prognostic value

Emerging data suggest that the RDW may also have prognostic value in nonhematologic diseases. In a retrospective study of 15,852 adult participants in the Third National Health and Nutrition Examination Survey (1988–1994), a higher RDW was associated with a higher risk of death, with the all-cause mortality rate increasing by 23% for every 1% increment in RDW.²

This correlation is particularly prominent in cardiac disorders. In 2 large retrospective studies of patients with symptomatic heart failure, a higher RDW was a strong predictor of morbidity and death (hazard ratio 1.17 per 1-standard deviation increase, P < .001), even stronger than more commonly used variables such as ejection fraction, New York Heart Association functional class, and renal function.³

In a retrospective analysis of 4,111 patients with myocardial infarction, the degree of RDW elevation correlated with the risk of repeat nonfatal myocardial infarction, coronary death, new symptomatic heart failure, and stroke.⁴

It is hypothesized that high RDW may reflect poor cell membrane integrity from altered cholesterol content, which in turn has deleterious effects on multiple organ systems and is therefore associated with adverse outcomes.⁵

Currently, using the RDW to assess prognosis remains investigational, and how best to interpret it in daily practice requires further study.

 

 

MEAN PLATELET VOLUME

The MPV, ie, the average size of platelets, is reported in femtoliters (fL). Because the MPV varies depending on the instrument used, each laboratory has a unique reference range, usually about 8 to 12 fL. The MPV must be interpreted in conjunction with the platelet count; the product of the MPV and platelet count is called the total platelet mass.

Using the MPV to find the cause of thrombocytopenia

The MPV can be used to help narrow the differential diagnosis of thrombocytopenia. For example, it is high in thrombocytopenia resulting from peripheral destruction, as in immune thrombocytopenic purpura. This is because as platelets are lost, thrombopoietin production increases and new, larger platelets are released from healthy megakaryocytes in an attempt to increase the total platelet mass.

In contrast, the MPV is low in patients with thrombocytopenia due to megakaryocyte hypoplasia, as malfunctioning megakaryocytes cannot maintain the total platelet mass, and any platelets produced remain small. This distinction can be obscured in the setting of splenomegaly, as larger platelets are more easily sequestered in the spleen and the MPV may therefore be low or normal.

The MPV can also be used to differentiate congenital thrombocytopenic disorders, which can be characterized by either a high MPV (eg, gray platelet syndrome, Bernard-Soulier syndrome) or a low MPV (eg, Wiskott-Aldrich syndrome) (Figure 2).

MPV may have prognostic value

Evidence suggests that the MPV also has potential prognostic value, particularly in vascular disease, as larger platelets are hypothesized to have increased hemostatic potential.

In a large meta-analysis of patients with coronary artery disease, a high MPV was associated with worse outcomes; the risk of death or myocardial infarction was 17% higher in those with a high MPV (the threshold ranged from 8.4 to 11.7 fL in the different studies) than in those with a low MPV.⁶

In a study of 213 patients with non-ST-segment elevation myocardial infarction, the risk of significant coronary artery disease was 4.18 times higher in patients with a high MPV and a high troponin level than in patients with a normal MPV and a high troponin.⁷ The authors suggested that a high MPV may help identify patients at highest risk of significant coronary artery disease who would benefit from invasive studies (ie, coronary angiography).

This correlation has also been observed in other forms of vascular disease. In 261 patients who underwent carotid angioplasty and stenting, an MPV higher than 10.1 fL was associated with a risk of in-stent restenosis more than 3 times higher.⁸

The MPV has also been found to be higher in patients with type 2 diabetes than in controls, particularly in those with microvascular complications such as retinopathy or microalbuminuria.⁹

Conversely, in patients with cancer, a low MPV appears to be associated with a poor prognosis. In a retrospective analysis of 236 patients with esophageal cancer, those who had an MPV of 7.4 fL or less had significantly shorter overall survival than patients with an MPV higher than 7.4 fL.¹⁰

A low MPV has also been associated with an increased risk of venous thromoboembolism in patients with cancer. In a prospective observational cohort study of 1,544 patients, the 2-year probability of venous thromboembolism was 9% in patients with an MPV less than 10.8 fL, compared with 5.5% in those with higher MPV values. The 2-year overall survival rate was also higher in patients with high MPV than in those with low MPV, at 64.7% vs 55.7%, respectively (P = .001).¹¹

But the MPV is far from a perfect clinical metric. Since its measurement is subject to significant laboratory variation, an abnormal value should always be confirmed with evaluation of a peripheral blood smear. Furthermore, it is unclear why a high MPV portends poor prognosis in patients without cancer, whereas the opposite is true in patients with cancer. Therefore, its role in prognostication remains investigational, and further studies are essential to determine its appropriate usefulness in clinical practice.¹²

NUCLEATED RED BLOOD CELL COUNT

NRBCs are immature red blood cell precursors not present in the circulation of healthy adults. During erythropoiesis, the common myeloid progenitor cell first differentiates into a proerythroblast; subsequently, the chromatin in the nucleus of the proerythroblast gradually condenses until it becomes an orthochromatic erythroblast, also known as a nucleated red cell (Figure 2). Once the nucleus is expelled, the cell is known as a reticulocyte, which ultimately becomes a mature erythrocyte.

Healthy newborns have circulating NRBCs that rapidly disappear within a few weeks of birth. However, NRBCs can return to the circulation in a variety of disease states.

Causes of NRBCs

Brisk hemolysis or rapid blood loss can cause NRBCs to be released into the blood as erythropoiesis increases in an attempt to compensate for acute anemia.

Damage or stress to the bone marrow also causes NRBCs to be released into the peripheral blood, as is often the case in hematologic diseases. In a study of 478 patients with hematologic diseases, the frequency of NRBC positivity at diagnosis was highest in patients with chronic myeloid leukemia (100%), acute leukemia (62%), and myelodysplastic syndromes (45%).¹³ NRBCs also appeared at higher frequencies during chemotherapy in other hematologic conditions, such as hemophagocytic lymphohistiocytosis.

The mechanism by which NRBCs are expelled from the bone marrow is unclear, though studies have suggested that inflammation or hypoxia or both cause increased hematopoietic stress, resulting in the release of immature red cells. Increased concentrations of inflammatory cytokines (interleukin 6 and interleukin 3) and erythropoietin in the plasma and decreased arterial oxygen partial tension have been reported in patients with circulating NRBCs.^14,15

Because they are associated with hematologic disorders, the finding of NRBCs should prompt evaluation of a peripheral smear to assess for abnormalities in other cell lines.

The NRBC count and prognosis

In critically ill patients, peripheral NRBCs can also indicate life-threatening conditions.

In a study of 421 adult intensive care patients, the in-hospital mortality rate was 42% in those with peripheral NRBCs vs 5.9% in those without them.¹⁶ Further, the higher the NRBC count and the more days that NRBCs were reported in the CBC, the higher the risk of death.

In adults with acute respiratory distress syndrome, the finding of any NRBCs in the peripheral blood was an independent risk factor for death, and an NRBC count higher than 220 cells/µL was associated with a more than 3-fold higher risk of death.¹⁷

Daily screening in patients in surgical intensive care units revealed that NRBCs appeared an average of 9 days before death, consistent with an early marker of impending decline.¹⁸

In another study,¹⁹ the risk of death within 90 days of hospital discharge was higher in NRBC-positive patients, reaching 21.9% in those who had a count higher than 200 cells/µL. The risk of unplanned hospital readmission within 30 days was also increased.

Leukoerythroblastosis

The combination of NRBCs and immature white blood cells (eg, myelocytes, metamyelocytes) is called leukoerythroblastosis.

Leukoerythroblastosis is classically seen in myelophthisic anemias in which hematopoietic cells in the marrow are displaced by fibrosis, tumor, or other space-occupying processes, but it can also occur in any situation of acute marrow stress, including critical illness.

In addition, leukoerythroblastosis appears in a rare complication of sickle cell hemoglobinopathies: bone marrow necrosis with fat embolism syndrome.^20,21 As the marrow necroses, fat emboli are released in the systemic circulation causing micro- and macrovascular occlusions and multiorgan failure. The largest case series in the literature reports 58 patients with bone marrow necrosis with fat embolism syndrome.²²

At our institution, we have seen 18 patients with this condition in the past 8 years, with the frequency of diagnosis increasing with heightened awareness of the disorder. We have found that leukoerythroblastosis is often an early marker of this unrecognized syndrome and can prompt emergency red cell exchange, which is considered to be lifesaving in this condition.²²

These examples and many others show that the presence of NRBCs in the CBC can serve as an important clinical warning.

OLD TESTS CAN STILL BE USEFUL

The CBC provides much more than simple cell counts; it is a rich collection of information related to each blood cell. These days, with new diagnostic tests and prognostic tools based on molecular analysis, it is important to not overlook the value of the tests clinicians have been ordering for generations.

The RDW, MPV, and NRBC count will not likely provide definitive or flawless diagnostic or prognostic information, but when understood and used correctly, they provide readily available, cost-effective, and useful data that can supplement and guide clinical decision-making. By understanding the CBC more fully, providers can maximize the truly complete nature of this routine laboratory test.

The complete blood cell count (CBC) is one of the most frequently ordered laboratory tests in both the inpatient and outpatient settings. Not long ago, the CBC required peering through a microscope and counting the red blood cells, white blood cells, and platelets. These 3 numbers are still the primary purpose of the test.

Now, with automated counters, the CBC report also contains other numbers that delineate characteristics of each cell type. For example:

The mean corpuscular volume is the average volume of red blood cells. Providers use it to classify anemia as either microcytic, normocytic, or macrocytic, each with its own differential diagnosis.

The differential white blood cell count provides absolute counts and relative percentages of each type of leukocyte. For example, the absolute neutrophil count is an important measure of immunocompetence.

But other values in the CBC may be overlooked, even though they can provide important information. Here, we highlight 3 of them:

• The red blood cell distribution width (RDW)
• The mean platelet volume (MPV)
• The nucleated red blood cell (NRBC) count.

In addition to describing their diagnostic utility, we also discuss emerging evidence of their potential prognostic significance in hematologic and nonhematologic disorders. By incorporating an awareness of their value in clinical practice, providers can maximize the usefulness of the CBC.

RED BLOOD CELL DISTRIBUTION WIDTH

The RDW is a measure of variation (anisocytosis) in the size of the circulating red cells. The term “width” is misleading, as the value is not derived from the width of the red blood cell, but rather from the width of the distribution curve of the corpuscular volume (Figure 1). Therefore, a normal RDW means that the cells are all about the same size, while a high RDW means they vary widely in size.

The RDW can be calculated either as a coefficient of variation, with a reference range of 11% to 16% depending on the laboratory, or, less often, as a standard deviation, with a reference range of 39 to 46 fL.

The RDW can differentiate between causes of anemia

A high RDW is often found in nutritional deficiencies of iron, vitamin B₁₂, and folate. This information is helpful in differentiating the cause of microcytic anemia, as a high RDW suggests iron-deficiency anemia while a normal RDW suggests thalassemia.¹ In iron deficiency, the RDW often rises before the mean corpuscular volume falls, serving as an early diagnostic clue.

The RDW can also be high after recent hemorrhage or rapid hemolysis, as the acute drop in hemoglobin results in increased production of reticulocytes, which are larger than mature erythrocytes.

Because a range of disorders can elevate the RDW, reviewing the peripheral blood smear is an important next step in the diagnostic evaluation, specifically looking for reticulocytes, microspherocytes, and other abnormal red blood cells contributing to the RDW elevation.

A normal RDW is less diagnostically useful. It indicates the red blood cells are of uniform size, but they may be uniformly small or large depending on how long the anemia has persisted. Since red cells circulate for only about 120 days, patients who have severe iron-deficiency anemia for months to years are expected to have a normal rather than a high RDW, as their red cells of normal size have all been replaced by microcytes.

A low RDW is not consistently associated with any hematologic disorder.

RDW may have prognostic value

Emerging data suggest that the RDW may also have prognostic value in nonhematologic diseases. In a retrospective study of 15,852 adult participants in the Third National Health and Nutrition Examination Survey (1988–1994), a higher RDW was associated with a higher risk of death, with the all-cause mortality rate increasing by 23% for every 1% increment in RDW.²

This correlation is particularly prominent in cardiac disorders. In 2 large retrospective studies of patients with symptomatic heart failure, a higher RDW was a strong predictor of morbidity and death (hazard ratio 1.17 per 1-standard deviation increase, P < .001), even stronger than more commonly used variables such as ejection fraction, New York Heart Association functional class, and renal function.³

In a retrospective analysis of 4,111 patients with myocardial infarction, the degree of RDW elevation correlated with the risk of repeat nonfatal myocardial infarction, coronary death, new symptomatic heart failure, and stroke.⁴

It is hypothesized that high RDW may reflect poor cell membrane integrity from altered cholesterol content, which in turn has deleterious effects on multiple organ systems and is therefore associated with adverse outcomes.⁵

Currently, using the RDW to assess prognosis remains investigational, and how best to interpret it in daily practice requires further study.

 

 

MEAN PLATELET VOLUME

The MPV, ie, the average size of platelets, is reported in femtoliters (fL). Because the MPV varies depending on the instrument used, each laboratory has a unique reference range, usually about 8 to 12 fL. The MPV must be interpreted in conjunction with the platelet count; the product of the MPV and platelet count is called the total platelet mass.

Using the MPV to find the cause of thrombocytopenia

The MPV can be used to help narrow the differential diagnosis of thrombocytopenia. For example, it is high in thrombocytopenia resulting from peripheral destruction, as in immune thrombocytopenic purpura. This is because as platelets are lost, thrombopoietin production increases and new, larger platelets are released from healthy megakaryocytes in an attempt to increase the total platelet mass.

In contrast, the MPV is low in patients with thrombocytopenia due to megakaryocyte hypoplasia, as malfunctioning megakaryocytes cannot maintain the total platelet mass, and any platelets produced remain small. This distinction can be obscured in the setting of splenomegaly, as larger platelets are more easily sequestered in the spleen and the MPV may therefore be low or normal.

The MPV can also be used to differentiate congenital thrombocytopenic disorders, which can be characterized by either a high MPV (eg, gray platelet syndrome, Bernard-Soulier syndrome) or a low MPV (eg, Wiskott-Aldrich syndrome) (Figure 2).

MPV may have prognostic value

Evidence suggests that the MPV also has potential prognostic value, particularly in vascular disease, as larger platelets are hypothesized to have increased hemostatic potential.

In a large meta-analysis of patients with coronary artery disease, a high MPV was associated with worse outcomes; the risk of death or myocardial infarction was 17% higher in those with a high MPV (the threshold ranged from 8.4 to 11.7 fL in the different studies) than in those with a low MPV.⁶

In a study of 213 patients with non-ST-segment elevation myocardial infarction, the risk of significant coronary artery disease was 4.18 times higher in patients with a high MPV and a high troponin level than in patients with a normal MPV and a high troponin.⁷ The authors suggested that a high MPV may help identify patients at highest risk of significant coronary artery disease who would benefit from invasive studies (ie, coronary angiography).

This correlation has also been observed in other forms of vascular disease. In 261 patients who underwent carotid angioplasty and stenting, an MPV higher than 10.1 fL was associated with a risk of in-stent restenosis more than 3 times higher.⁸

The MPV has also been found to be higher in patients with type 2 diabetes than in controls, particularly in those with microvascular complications such as retinopathy or microalbuminuria.⁹

Conversely, in patients with cancer, a low MPV appears to be associated with a poor prognosis. In a retrospective analysis of 236 patients with esophageal cancer, those who had an MPV of 7.4 fL or less had significantly shorter overall survival than patients with an MPV higher than 7.4 fL.¹⁰

A low MPV has also been associated with an increased risk of venous thromoboembolism in patients with cancer. In a prospective observational cohort study of 1,544 patients, the 2-year probability of venous thromboembolism was 9% in patients with an MPV less than 10.8 fL, compared with 5.5% in those with higher MPV values. The 2-year overall survival rate was also higher in patients with high MPV than in those with low MPV, at 64.7% vs 55.7%, respectively (P = .001).¹¹

But the MPV is far from a perfect clinical metric. Since its measurement is subject to significant laboratory variation, an abnormal value should always be confirmed with evaluation of a peripheral blood smear. Furthermore, it is unclear why a high MPV portends poor prognosis in patients without cancer, whereas the opposite is true in patients with cancer. Therefore, its role in prognostication remains investigational, and further studies are essential to determine its appropriate usefulness in clinical practice.¹²

NUCLEATED RED BLOOD CELL COUNT

NRBCs are immature red blood cell precursors not present in the circulation of healthy adults. During erythropoiesis, the common myeloid progenitor cell first differentiates into a proerythroblast; subsequently, the chromatin in the nucleus of the proerythroblast gradually condenses until it becomes an orthochromatic erythroblast, also known as a nucleated red cell (Figure 2). Once the nucleus is expelled, the cell is known as a reticulocyte, which ultimately becomes a mature erythrocyte.

Healthy newborns have circulating NRBCs that rapidly disappear within a few weeks of birth. However, NRBCs can return to the circulation in a variety of disease states.

Causes of NRBCs

Brisk hemolysis or rapid blood loss can cause NRBCs to be released into the blood as erythropoiesis increases in an attempt to compensate for acute anemia.

Damage or stress to the bone marrow also causes NRBCs to be released into the peripheral blood, as is often the case in hematologic diseases. In a study of 478 patients with hematologic diseases, the frequency of NRBC positivity at diagnosis was highest in patients with chronic myeloid leukemia (100%), acute leukemia (62%), and myelodysplastic syndromes (45%).¹³ NRBCs also appeared at higher frequencies during chemotherapy in other hematologic conditions, such as hemophagocytic lymphohistiocytosis.

The mechanism by which NRBCs are expelled from the bone marrow is unclear, though studies have suggested that inflammation or hypoxia or both cause increased hematopoietic stress, resulting in the release of immature red cells. Increased concentrations of inflammatory cytokines (interleukin 6 and interleukin 3) and erythropoietin in the plasma and decreased arterial oxygen partial tension have been reported in patients with circulating NRBCs.^14,15

Because they are associated with hematologic disorders, the finding of NRBCs should prompt evaluation of a peripheral smear to assess for abnormalities in other cell lines.

The NRBC count and prognosis

In critically ill patients, peripheral NRBCs can also indicate life-threatening conditions.

In a study of 421 adult intensive care patients, the in-hospital mortality rate was 42% in those with peripheral NRBCs vs 5.9% in those without them.¹⁶ Further, the higher the NRBC count and the more days that NRBCs were reported in the CBC, the higher the risk of death.

In adults with acute respiratory distress syndrome, the finding of any NRBCs in the peripheral blood was an independent risk factor for death, and an NRBC count higher than 220 cells/µL was associated with a more than 3-fold higher risk of death.¹⁷

Daily screening in patients in surgical intensive care units revealed that NRBCs appeared an average of 9 days before death, consistent with an early marker of impending decline.¹⁸

In another study,¹⁹ the risk of death within 90 days of hospital discharge was higher in NRBC-positive patients, reaching 21.9% in those who had a count higher than 200 cells/µL. The risk of unplanned hospital readmission within 30 days was also increased.

Leukoerythroblastosis

The combination of NRBCs and immature white blood cells (eg, myelocytes, metamyelocytes) is called leukoerythroblastosis.

Leukoerythroblastosis is classically seen in myelophthisic anemias in which hematopoietic cells in the marrow are displaced by fibrosis, tumor, or other space-occupying processes, but it can also occur in any situation of acute marrow stress, including critical illness.

In addition, leukoerythroblastosis appears in a rare complication of sickle cell hemoglobinopathies: bone marrow necrosis with fat embolism syndrome.^20,21 As the marrow necroses, fat emboli are released in the systemic circulation causing micro- and macrovascular occlusions and multiorgan failure. The largest case series in the literature reports 58 patients with bone marrow necrosis with fat embolism syndrome.²²

At our institution, we have seen 18 patients with this condition in the past 8 years, with the frequency of diagnosis increasing with heightened awareness of the disorder. We have found that leukoerythroblastosis is often an early marker of this unrecognized syndrome and can prompt emergency red cell exchange, which is considered to be lifesaving in this condition.²²

These examples and many others show that the presence of NRBCs in the CBC can serve as an important clinical warning.

OLD TESTS CAN STILL BE USEFUL

The CBC provides much more than simple cell counts; it is a rich collection of information related to each blood cell. These days, with new diagnostic tests and prognostic tools based on molecular analysis, it is important to not overlook the value of the tests clinicians have been ordering for generations.

The RDW, MPV, and NRBC count will not likely provide definitive or flawless diagnostic or prognostic information, but when understood and used correctly, they provide readily available, cost-effective, and useful data that can supplement and guide clinical decision-making. By understanding the CBC more fully, providers can maximize the truly complete nature of this routine laboratory test.

The complete blood cell count (CBC) is one of the most frequently ordered laboratory tests in both the inpatient and outpatient settings. Not long ago, the CBC required peering through a microscope and counting the red blood cells, white blood cells, and platelets. These 3 numbers are still the primary purpose of the test.

Now, with automated counters, the CBC report also contains other numbers that delineate characteristics of each cell type. For example:

The mean corpuscular volume is the average volume of red blood cells. Providers use it to classify anemia as either microcytic, normocytic, or macrocytic, each with its own differential diagnosis.

The differential white blood cell count provides absolute counts and relative percentages of each type of leukocyte. For example, the absolute neutrophil count is an important measure of immunocompetence.

But other values in the CBC may be overlooked, even though they can provide important information. Here, we highlight 3 of them:

• The red blood cell distribution width (RDW)
• The mean platelet volume (MPV)
• The nucleated red blood cell (NRBC) count.

In addition to describing their diagnostic utility, we also discuss emerging evidence of their potential prognostic significance in hematologic and nonhematologic disorders. By incorporating an awareness of their value in clinical practice, providers can maximize the usefulness of the CBC.

RED BLOOD CELL DISTRIBUTION WIDTH

The RDW is a measure of variation (anisocytosis) in the size of the circulating red cells. The term “width” is misleading, as the value is not derived from the width of the red blood cell, but rather from the width of the distribution curve of the corpuscular volume (Figure 1). Therefore, a normal RDW means that the cells are all about the same size, while a high RDW means they vary widely in size.

The RDW can be calculated either as a coefficient of variation, with a reference range of 11% to 16% depending on the laboratory, or, less often, as a standard deviation, with a reference range of 39 to 46 fL.

The RDW can differentiate between causes of anemia

A high RDW is often found in nutritional deficiencies of iron, vitamin B₁₂, and folate. This information is helpful in differentiating the cause of microcytic anemia, as a high RDW suggests iron-deficiency anemia while a normal RDW suggests thalassemia.¹ In iron deficiency, the RDW often rises before the mean corpuscular volume falls, serving as an early diagnostic clue.

The RDW can also be high after recent hemorrhage or rapid hemolysis, as the acute drop in hemoglobin results in increased production of reticulocytes, which are larger than mature erythrocytes.

Because a range of disorders can elevate the RDW, reviewing the peripheral blood smear is an important next step in the diagnostic evaluation, specifically looking for reticulocytes, microspherocytes, and other abnormal red blood cells contributing to the RDW elevation.

A normal RDW is less diagnostically useful. It indicates the red blood cells are of uniform size, but they may be uniformly small or large depending on how long the anemia has persisted. Since red cells circulate for only about 120 days, patients who have severe iron-deficiency anemia for months to years are expected to have a normal rather than a high RDW, as their red cells of normal size have all been replaced by microcytes.

A low RDW is not consistently associated with any hematologic disorder.

RDW may have prognostic value

Emerging data suggest that the RDW may also have prognostic value in nonhematologic diseases. In a retrospective study of 15,852 adult participants in the Third National Health and Nutrition Examination Survey (1988–1994), a higher RDW was associated with a higher risk of death, with the all-cause mortality rate increasing by 23% for every 1% increment in RDW.²

This correlation is particularly prominent in cardiac disorders. In 2 large retrospective studies of patients with symptomatic heart failure, a higher RDW was a strong predictor of morbidity and death (hazard ratio 1.17 per 1-standard deviation increase, P < .001), even stronger than more commonly used variables such as ejection fraction, New York Heart Association functional class, and renal function.³

In a retrospective analysis of 4,111 patients with myocardial infarction, the degree of RDW elevation correlated with the risk of repeat nonfatal myocardial infarction, coronary death, new symptomatic heart failure, and stroke.⁴

It is hypothesized that high RDW may reflect poor cell membrane integrity from altered cholesterol content, which in turn has deleterious effects on multiple organ systems and is therefore associated with adverse outcomes.⁵

Currently, using the RDW to assess prognosis remains investigational, and how best to interpret it in daily practice requires further study.

 

 

MEAN PLATELET VOLUME

The MPV, ie, the average size of platelets, is reported in femtoliters (fL). Because the MPV varies depending on the instrument used, each laboratory has a unique reference range, usually about 8 to 12 fL. The MPV must be interpreted in conjunction with the platelet count; the product of the MPV and platelet count is called the total platelet mass.

Using the MPV to find the cause of thrombocytopenia

The MPV can be used to help narrow the differential diagnosis of thrombocytopenia. For example, it is high in thrombocytopenia resulting from peripheral destruction, as in immune thrombocytopenic purpura. This is because as platelets are lost, thrombopoietin production increases and new, larger platelets are released from healthy megakaryocytes in an attempt to increase the total platelet mass.

In contrast, the MPV is low in patients with thrombocytopenia due to megakaryocyte hypoplasia, as malfunctioning megakaryocytes cannot maintain the total platelet mass, and any platelets produced remain small. This distinction can be obscured in the setting of splenomegaly, as larger platelets are more easily sequestered in the spleen and the MPV may therefore be low or normal.

The MPV can also be used to differentiate congenital thrombocytopenic disorders, which can be characterized by either a high MPV (eg, gray platelet syndrome, Bernard-Soulier syndrome) or a low MPV (eg, Wiskott-Aldrich syndrome) (Figure 2).

MPV may have prognostic value

Evidence suggests that the MPV also has potential prognostic value, particularly in vascular disease, as larger platelets are hypothesized to have increased hemostatic potential.

In a large meta-analysis of patients with coronary artery disease, a high MPV was associated with worse outcomes; the risk of death or myocardial infarction was 17% higher in those with a high MPV (the threshold ranged from 8.4 to 11.7 fL in the different studies) than in those with a low MPV.⁶

In a study of 213 patients with non-ST-segment elevation myocardial infarction, the risk of significant coronary artery disease was 4.18 times higher in patients with a high MPV and a high troponin level than in patients with a normal MPV and a high troponin.⁷ The authors suggested that a high MPV may help identify patients at highest risk of significant coronary artery disease who would benefit from invasive studies (ie, coronary angiography).

This correlation has also been observed in other forms of vascular disease. In 261 patients who underwent carotid angioplasty and stenting, an MPV higher than 10.1 fL was associated with a risk of in-stent restenosis more than 3 times higher.⁸

The MPV has also been found to be higher in patients with type 2 diabetes than in controls, particularly in those with microvascular complications such as retinopathy or microalbuminuria.⁹

Conversely, in patients with cancer, a low MPV appears to be associated with a poor prognosis. In a retrospective analysis of 236 patients with esophageal cancer, those who had an MPV of 7.4 fL or less had significantly shorter overall survival than patients with an MPV higher than 7.4 fL.¹⁰

A low MPV has also been associated with an increased risk of venous thromoboembolism in patients with cancer. In a prospective observational cohort study of 1,544 patients, the 2-year probability of venous thromboembolism was 9% in patients with an MPV less than 10.8 fL, compared with 5.5% in those with higher MPV values. The 2-year overall survival rate was also higher in patients with high MPV than in those with low MPV, at 64.7% vs 55.7%, respectively (P = .001).¹¹

But the MPV is far from a perfect clinical metric. Since its measurement is subject to significant laboratory variation, an abnormal value should always be confirmed with evaluation of a peripheral blood smear. Furthermore, it is unclear why a high MPV portends poor prognosis in patients without cancer, whereas the opposite is true in patients with cancer. Therefore, its role in prognostication remains investigational, and further studies are essential to determine its appropriate usefulness in clinical practice.¹²

NUCLEATED RED BLOOD CELL COUNT

NRBCs are immature red blood cell precursors not present in the circulation of healthy adults. During erythropoiesis, the common myeloid progenitor cell first differentiates into a proerythroblast; subsequently, the chromatin in the nucleus of the proerythroblast gradually condenses until it becomes an orthochromatic erythroblast, also known as a nucleated red cell (Figure 2). Once the nucleus is expelled, the cell is known as a reticulocyte, which ultimately becomes a mature erythrocyte.

Healthy newborns have circulating NRBCs that rapidly disappear within a few weeks of birth. However, NRBCs can return to the circulation in a variety of disease states.

Causes of NRBCs

Brisk hemolysis or rapid blood loss can cause NRBCs to be released into the blood as erythropoiesis increases in an attempt to compensate for acute anemia.

Damage or stress to the bone marrow also causes NRBCs to be released into the peripheral blood, as is often the case in hematologic diseases. In a study of 478 patients with hematologic diseases, the frequency of NRBC positivity at diagnosis was highest in patients with chronic myeloid leukemia (100%), acute leukemia (62%), and myelodysplastic syndromes (45%).¹³ NRBCs also appeared at higher frequencies during chemotherapy in other hematologic conditions, such as hemophagocytic lymphohistiocytosis.

The mechanism by which NRBCs are expelled from the bone marrow is unclear, though studies have suggested that inflammation or hypoxia or both cause increased hematopoietic stress, resulting in the release of immature red cells. Increased concentrations of inflammatory cytokines (interleukin 6 and interleukin 3) and erythropoietin in the plasma and decreased arterial oxygen partial tension have been reported in patients with circulating NRBCs.^14,15

Because they are associated with hematologic disorders, the finding of NRBCs should prompt evaluation of a peripheral smear to assess for abnormalities in other cell lines.

The NRBC count and prognosis

In critically ill patients, peripheral NRBCs can also indicate life-threatening conditions.

In a study of 421 adult intensive care patients, the in-hospital mortality rate was 42% in those with peripheral NRBCs vs 5.9% in those without them.¹⁶ Further, the higher the NRBC count and the more days that NRBCs were reported in the CBC, the higher the risk of death.

In adults with acute respiratory distress syndrome, the finding of any NRBCs in the peripheral blood was an independent risk factor for death, and an NRBC count higher than 220 cells/µL was associated with a more than 3-fold higher risk of death.¹⁷

Daily screening in patients in surgical intensive care units revealed that NRBCs appeared an average of 9 days before death, consistent with an early marker of impending decline.¹⁸

In another study,¹⁹ the risk of death within 90 days of hospital discharge was higher in NRBC-positive patients, reaching 21.9% in those who had a count higher than 200 cells/µL. The risk of unplanned hospital readmission within 30 days was also increased.

Leukoerythroblastosis

The combination of NRBCs and immature white blood cells (eg, myelocytes, metamyelocytes) is called leukoerythroblastosis.

Leukoerythroblastosis is classically seen in myelophthisic anemias in which hematopoietic cells in the marrow are displaced by fibrosis, tumor, or other space-occupying processes, but it can also occur in any situation of acute marrow stress, including critical illness.

In addition, leukoerythroblastosis appears in a rare complication of sickle cell hemoglobinopathies: bone marrow necrosis with fat embolism syndrome.^20,21 As the marrow necroses, fat emboli are released in the systemic circulation causing micro- and macrovascular occlusions and multiorgan failure. The largest case series in the literature reports 58 patients with bone marrow necrosis with fat embolism syndrome.²²

At our institution, we have seen 18 patients with this condition in the past 8 years, with the frequency of diagnosis increasing with heightened awareness of the disorder. We have found that leukoerythroblastosis is often an early marker of this unrecognized syndrome and can prompt emergency red cell exchange, which is considered to be lifesaving in this condition.²²

These examples and many others show that the presence of NRBCs in the CBC can serve as an important clinical warning.

OLD TESTS CAN STILL BE USEFUL

The CBC provides much more than simple cell counts; it is a rich collection of information related to each blood cell. These days, with new diagnostic tests and prognostic tools based on molecular analysis, it is important to not overlook the value of the tests clinicians have been ordering for generations.

The RDW, MPV, and NRBC count will not likely provide definitive or flawless diagnostic or prognostic information, but when understood and used correctly, they provide readily available, cost-effective, and useful data that can supplement and guide clinical decision-making. By understanding the CBC more fully, providers can maximize the truly complete nature of this routine laboratory test.

Staging of liver fibrosis, important for determining prognosis in patients with chronic liver disease and for the need to start screening for complications of cirrhosis, was traditionally done only by liver biopsy. While biopsy is still the gold standard method to stage fibrosis, noninvasive methods have been developed that can also assess disease severity.

This article briefly reviews the epidemiology and physiology of chronic liver disease and the traditional role of liver biopsy. Pros and cons of alternative fibrosis assessment methods are discussed, with a focus on their utility for patients with nonalcoholic fatty liver disease (NAFLD) and hepatitis C virus (HCV) infection.

CHRONIC LIVER DISEASE: A HUGE HEALTH BURDEN

Chronic liver disease is associated with enormous health and financial costs in the United States. Its prevalence is about 15%,¹ and it is the 12th leading cause of death.² Hospital costs are estimated at about $4 billion annually.³

The most common causes of chronic liver disease are NAFLD (which may be present in up to one-third of the US population and is increasing with the epidemic of obesity), its aggressive variant, nonalcoholic steatohepatitis (NASH) (present in about 3% of the population), and HCV infection (1%).^4,5

Since direct-acting antiviral agents were introduced, HCV infection dropped from being the leading cause of liver transplant to third place.⁶ But at the same time, the number of patients on the transplant waiting list who have NASH has risen faster than for any other cause of chronic liver disease.⁷

FIBROSIS: A KEY INDICATOR OF DISEASE SEVERITY

With any form of liver disease, collagen is deposited in hepatic lobules over time, a process called fibrosis. Both HCV infection and NASH involve necroinflammation in the liver, hepatocyte apoptosis, and activation of stellate cells, leading to progressive collagen deposition in hepatic lobules. Fibrosis typically starts in the region of the central vein and portal tracts and eventually extends to other areas of the lobule.

Determining fibrosis severity is critical when a patient is diagnosed with chronic liver disease, as it predicts long-term clinical outcomes and death in HCV⁸ and NAFLD.⁹ Different staging systems have been developed to reflect the degree of fibrosis, based on its distribution as seen on liver biopsy (Table 1, Figure 1).

In HCV infection, advanced fibrosis is defined as either stage 4 to 6 using the Ishak system¹⁰ or stage 3 to 4 using the Meta-analysis of Histological Data in Viral Hepatitis (METAVIR) system.¹¹

In NAFLD, advanced fibrosis is defined as stage 3 to 4 using the NASH Clinical Research Network system.¹²

Staging fibrosis is also important so that patients with cirrhosis can be identified early to begin screening for hepatocellular carcinoma and esophageal varices to reduce the risks of illness and death. In addition, insurance companies often require documentation of fibrosis stage before treating HCV with the new direct-acting antiviral agents.

LIVER BIOPSY IS STILL THE GOLD STANDARD

Although invasive, liver biopsy remains the gold standard for determining fibrosis stage. Liver biopsies were performed “blindly” (without imaging) until the 1990s, but imaging-guided biopsy using ultrasonography was then developed, which entailed less pain and lower complication and hospitalization rates. Slightly more hepatic tissue is obtained with guided liver biopsy, but the difference was deemed clinically insignificant.¹³ Concern initially arose about the added cost involved with imaging, but imaging-guided biopsy was actually found to be more cost-effective.¹⁴

In the 2000s, transjugular liver biopsy via the right internal jugular vein became available. This method was originally used primarily in patients with ascites or significant coagulopathy. At first, there were concerns about the adequacy of specimens obtained to make an accurate diagnosis or establish fibrosis stage, but this limitation was overcome with improved techniques.^15,16 Transjugular liver biopsy has the additional advantage of enabling one to measure the hepatic venous pressure gradient, which also has prognostic significance; a gradient greater than 10 mm Hg is associated with worse prognosis.¹⁷

Disadvantages of biopsy: Complications, sampling errors

Liver biopsy has disadvantages. Reported rates of complications necessitating hospitalization using the blind method were as high as 6% in the 1970s,¹⁸ dropping to 3.2% in a 1993 study.¹⁹ Bleeding remains the most worrisome complication. With the transjugular method, major and minor complication rates are less than 1% and 7%, respectively.^15,16 Complication rates with imaging-guided biopsy are also low.

Liver biopsy is also prone to sampling error. The number of portal tracts obtained in the biopsy correlates with the accuracy of fibrosis staging, and smaller samples may lead to underestimating fibrosis stage. In patients with HCV, samples more than 15 mm long led to accurate staging diagnosis in 65% of patients, and those longer than 25 mm conferred 75% accuracy.²⁰ Also, different stages can be diagnosed from samples obtained from separate locations in the liver, although rarely is the difference more than a single stage.²¹

Histologic evaluation of liver biopsies is operator-dependent. Although significant interobserver variation has been reported for degree of inflammation, there tends to be good concordance for fibrosis staging.^22,23

 

 

STAGING BASED ON DEMOGRAPHIC AND LABORATORY VARIABLES

Several scores based on patient characteristics and laboratory values have been developed for assessing liver fibrosis and have been specifically validated for HCV infection, NAFLD, or both. They can serve as inexpensive initial screening tests for the presence or absence of advanced fibrosis.

FIB-4 index for HCV, NAFLD

The FIB-4 index predicts the presence of advanced fibrosis using, as its name indicates, a combination of 4 factors in fibrosis: age, platelet count, and the levels of aspartate aminotransferase (AST) and alanine aminotransferase (ALT), according to the formula:

FIB-4 index = (age × AST [U/L]) /
(platelet count [× 10⁹/L] × √ALT [U/L]).

The index was derived from data from 832 patients co-infected with HCV and human immunodeficiency virus.²⁴ The Ishak staging system¹⁰ for fibrosis on liver biopsy was used for confirmation, with stage 4 to 6 defined as advanced fibrosis. A cutoff value of more than 3.25 had a positive predictive value of 65% for advanced fibrosis, and to exclude advanced fibrosis, a cutoff value of less than 1.45 had a negative predictive value of 90%.

The FIB-4 index has since been validated in patients with HCV infection²⁵ and NAFLD.²⁶ In a subsequent study in 142 patients with NAFLD, the FIB-4 index was more accurate in diagnosing advanced fibrosis than the other noninvasive prediction models discussed below.²⁷

NAFLD fibrosis score

The NAFLD fibrosis score, constructed and validated only in patients with biopsy-confirmed NAFLD, incorporates age, body mass index, presence of diabetes or prediabetes, albumin level, platelet count, and AST and ALT levels.

A group of 480 patients was used to construct the score, and 253 patients were used to validate it. Using the high cutoff value of 0.676, the presence of advanced fibrosis was diagnosed with a positive predictive value of 90% in the group used to construct the model (82% in the validation group). Using the low cutoff score of –1.455, advanced fibrosis could be excluded with a negative predictive value of 93% in the construction group and 88% in the validation group.²⁸ A score between the cutoff values merits liver biopsy to determine fibrosis stage. The score is more accurate in patients with diabetes.²⁹ When used by primary care physicians, the NAFLD fibrosis score is more cost-effective than transient elastography and liver biopsy for accurately predicting advanced fibrosis.³⁰

AST-to-platelet ratio index score for HCV, NAFLD

The AST-to-platelet ratio index (APRI) score was developed in 2003 using a cohort of 270 patients with HCV and liver biopsy as the standard. A cutoff value of less than or equal to 0.5 had a negative predictive value of 86% for the absence of significant fibrosis, while a score of more than 1.5 detected the presence of significant fibrosis with a positive predictive value of 88%.³¹ The APRI score was subsequently validated for NAFLD.^27,32

FibroSure uses a patented formula

FibroSure (LabCorp; labcorp.com) uses a patented mathematical formula that takes into account age, sex, and levels of gamma-glutamyl transferase, total bilirubin, haptoglobin, apolipoprotein-A, and alpha-2 macroglobulin to assess fibrosis. Developed in 2001 for use in patients with HCV infection, it was reported to have a positive predictive value of greater than 90% and a negative predictive value of 100% for clinically significant fibrosis, defined as stage 2 to 4 based on the METAVIR staging system in the prediction model.³³ The use of FibroSure in patients with HCV was subsequently validated in various meta-analyses and systematic reviews.^34,35 It is less accurate in patients with normal ALT levels.³⁶

FibroSure also has good accuracy for predicting fibrosis stage in chronic liver disease due to other causes, including NAFLD.³⁷

The prediction models discussed above use routine laboratory tests for chronic liver disease and thus are inexpensive. The high cost of additional testing needed for FibroSure, coupled with the risk of misdiagnosis, makes its cost-effectiveness questionable.³⁸

 

 

IMAGING TO PREDICT FIBROSIS STAGE

Conventional ultrasonography (with or without vascular imaging) and computed tomography can detect cirrhosis on the basis of certain imaging characteristics,^39,40 including the nodular contour of the liver, caudate lobe hypertrophy, ascites, reversal of blood flow in the portal vein, and splenomegaly. However, they cannot detect fibrosis in its early stages.

The 3 methods discussed below provide more accurate fibrosis staging by measuring the velocity of shear waves sent across hepatic tissue. Because shear-wave velocity increases with liver stiffness, the fibrosis stage can be estimated from this information.⁴¹

Transient elastography

Transient elastography uses a special ultrasound transducer. It is highly accurate for predicting advanced fibrosis for almost all causes of chronic liver disease, including HCV infection^42,43 and NAFLD.⁴⁴ The cutoff values of wave velocity to estimate fibrosis stage differ by liver disease etiology.

Transient elastography should not be used to evaluate fibrosis in patients with acute hepatitis, which transiently increases liver stiffness, resulting in a falsely high fibrosis stage diagnosis.⁴⁵ It is also not a good method for evaluating fibrosis in patients with biliary obstruction or extrahepatic venous congestion. Because liver stiffness can increase after eating,⁴⁶ the test should be done under fasting conditions.

A significant limitation of transient elastography has been its poor accuracy in patients with obesity.⁴⁷ This has been largely overcome with the use of a more powerful (XL) probe but is still a limitation for those with morbid obesity.⁴⁸ Because many patients with NAFLD are obese, this limitation can be significant.

Transient elastography has gained popularity for evaluating fibrosis in patients with chronic liver disease for multiple reasons: it is cost-effective and results are highly reproducible, with low variation in results among different observers and in individual observers.⁴⁹ Combined with a platelet count, it can also be used to detect the development of clinically significant portal hypertension in patients with cirrhosis, thus determining the need to screen for esophageal varices using endoscopy.⁵⁰ Screening endoscopy can be avoided in patients whose liver stiffness remains below 20 kPa or whose platelet count is above 150 × 10⁹/L.

Acoustic radiation force imaging

Unlike transient elastography, which requires a separate transducer probe to assess shear- wave velocity, acoustic radiation force imaging uses the same transducer for both this function and imaging. Different image modes are available when testing for liver stiffness, so a region of interest that is optimal for avoiding vascular structures or masses can be selected, increasing accuracy.⁵¹

Acoustic radiation force imaging has been tested in different causes of chronic liver disease, including HCV and NAFLD,⁵² with accuracy similar to that of transient elastography.⁵³ For overweight and obese patients, acoustic radiation force imaging is more accurate than transient elastography using the XL probe.⁵⁴ However, this method is still new, and we need more data to support using one method over the other.

Magnetic resonance elastography

Magnetic resonance elastography uses a special transducer placed under the rib cage to transmit shear waves concurrently with magnetic resonance imaging. It has been tested in patients with HCV and NAFLD and has been found to have better diagnostic accuracy than transient elastography and acoustic radiation force imaging.^55,56 Patients must be fasting for better diagnostic accuracy⁵⁷ and must hold their breath while elastography is performed. The need for breath-holding and the high cost limit the use of this method for assessing fibrosis.

BOTTOM LINE FOR ASSESSING FIBROSIS

Although liver biopsy remains the gold standard for accurately determining fibrosis stage, noninvasive methods, especially imaging techniques, are fast evolving. Guidelines recommend using transient elastography to determine fibrosis stage noninvasively in patients with HCV,⁵⁸ but a similar recommendation cannot be made for NAFLD with available data. For NAFLD, combined elastography and NAFLD fibrosis score are recommended to determine the need for a liver biopsy (Figure 2).⁵⁹ Currently, we recommend using a combination of the scores discussed above and the imaging tests.

Staging of liver fibrosis, important for determining prognosis in patients with chronic liver disease and for the need to start screening for complications of cirrhosis, was traditionally done only by liver biopsy. While biopsy is still the gold standard method to stage fibrosis, noninvasive methods have been developed that can also assess disease severity.

This article briefly reviews the epidemiology and physiology of chronic liver disease and the traditional role of liver biopsy. Pros and cons of alternative fibrosis assessment methods are discussed, with a focus on their utility for patients with nonalcoholic fatty liver disease (NAFLD) and hepatitis C virus (HCV) infection.

CHRONIC LIVER DISEASE: A HUGE HEALTH BURDEN

Chronic liver disease is associated with enormous health and financial costs in the United States. Its prevalence is about 15%,¹ and it is the 12th leading cause of death.² Hospital costs are estimated at about $4 billion annually.³

The most common causes of chronic liver disease are NAFLD (which may be present in up to one-third of the US population and is increasing with the epidemic of obesity), its aggressive variant, nonalcoholic steatohepatitis (NASH) (present in about 3% of the population), and HCV infection (1%).^4,5

Since direct-acting antiviral agents were introduced, HCV infection dropped from being the leading cause of liver transplant to third place.⁶ But at the same time, the number of patients on the transplant waiting list who have NASH has risen faster than for any other cause of chronic liver disease.⁷

FIBROSIS: A KEY INDICATOR OF DISEASE SEVERITY

With any form of liver disease, collagen is deposited in hepatic lobules over time, a process called fibrosis. Both HCV infection and NASH involve necroinflammation in the liver, hepatocyte apoptosis, and activation of stellate cells, leading to progressive collagen deposition in hepatic lobules. Fibrosis typically starts in the region of the central vein and portal tracts and eventually extends to other areas of the lobule.

Determining fibrosis severity is critical when a patient is diagnosed with chronic liver disease, as it predicts long-term clinical outcomes and death in HCV⁸ and NAFLD.⁹ Different staging systems have been developed to reflect the degree of fibrosis, based on its distribution as seen on liver biopsy (Table 1, Figure 1).

In HCV infection, advanced fibrosis is defined as either stage 4 to 6 using the Ishak system¹⁰ or stage 3 to 4 using the Meta-analysis of Histological Data in Viral Hepatitis (METAVIR) system.¹¹

In NAFLD, advanced fibrosis is defined as stage 3 to 4 using the NASH Clinical Research Network system.¹²

Staging fibrosis is also important so that patients with cirrhosis can be identified early to begin screening for hepatocellular carcinoma and esophageal varices to reduce the risks of illness and death. In addition, insurance companies often require documentation of fibrosis stage before treating HCV with the new direct-acting antiviral agents.

LIVER BIOPSY IS STILL THE GOLD STANDARD

Although invasive, liver biopsy remains the gold standard for determining fibrosis stage. Liver biopsies were performed “blindly” (without imaging) until the 1990s, but imaging-guided biopsy using ultrasonography was then developed, which entailed less pain and lower complication and hospitalization rates. Slightly more hepatic tissue is obtained with guided liver biopsy, but the difference was deemed clinically insignificant.¹³ Concern initially arose about the added cost involved with imaging, but imaging-guided biopsy was actually found to be more cost-effective.¹⁴

In the 2000s, transjugular liver biopsy via the right internal jugular vein became available. This method was originally used primarily in patients with ascites or significant coagulopathy. At first, there were concerns about the adequacy of specimens obtained to make an accurate diagnosis or establish fibrosis stage, but this limitation was overcome with improved techniques.^15,16 Transjugular liver biopsy has the additional advantage of enabling one to measure the hepatic venous pressure gradient, which also has prognostic significance; a gradient greater than 10 mm Hg is associated with worse prognosis.¹⁷

Disadvantages of biopsy: Complications, sampling errors

Liver biopsy has disadvantages. Reported rates of complications necessitating hospitalization using the blind method were as high as 6% in the 1970s,¹⁸ dropping to 3.2% in a 1993 study.¹⁹ Bleeding remains the most worrisome complication. With the transjugular method, major and minor complication rates are less than 1% and 7%, respectively.^15,16 Complication rates with imaging-guided biopsy are also low.

Liver biopsy is also prone to sampling error. The number of portal tracts obtained in the biopsy correlates with the accuracy of fibrosis staging, and smaller samples may lead to underestimating fibrosis stage. In patients with HCV, samples more than 15 mm long led to accurate staging diagnosis in 65% of patients, and those longer than 25 mm conferred 75% accuracy.²⁰ Also, different stages can be diagnosed from samples obtained from separate locations in the liver, although rarely is the difference more than a single stage.²¹

Histologic evaluation of liver biopsies is operator-dependent. Although significant interobserver variation has been reported for degree of inflammation, there tends to be good concordance for fibrosis staging.^22,23

 

 

STAGING BASED ON DEMOGRAPHIC AND LABORATORY VARIABLES

Several scores based on patient characteristics and laboratory values have been developed for assessing liver fibrosis and have been specifically validated for HCV infection, NAFLD, or both. They can serve as inexpensive initial screening tests for the presence or absence of advanced fibrosis.

FIB-4 index for HCV, NAFLD

The FIB-4 index predicts the presence of advanced fibrosis using, as its name indicates, a combination of 4 factors in fibrosis: age, platelet count, and the levels of aspartate aminotransferase (AST) and alanine aminotransferase (ALT), according to the formula:

FIB-4 index = (age × AST [U/L]) /
(platelet count [× 10⁹/L] × √ALT [U/L]).

The index was derived from data from 832 patients co-infected with HCV and human immunodeficiency virus.²⁴ The Ishak staging system¹⁰ for fibrosis on liver biopsy was used for confirmation, with stage 4 to 6 defined as advanced fibrosis. A cutoff value of more than 3.25 had a positive predictive value of 65% for advanced fibrosis, and to exclude advanced fibrosis, a cutoff value of less than 1.45 had a negative predictive value of 90%.

The FIB-4 index has since been validated in patients with HCV infection²⁵ and NAFLD.²⁶ In a subsequent study in 142 patients with NAFLD, the FIB-4 index was more accurate in diagnosing advanced fibrosis than the other noninvasive prediction models discussed below.²⁷

NAFLD fibrosis score

The NAFLD fibrosis score, constructed and validated only in patients with biopsy-confirmed NAFLD, incorporates age, body mass index, presence of diabetes or prediabetes, albumin level, platelet count, and AST and ALT levels.

A group of 480 patients was used to construct the score, and 253 patients were used to validate it. Using the high cutoff value of 0.676, the presence of advanced fibrosis was diagnosed with a positive predictive value of 90% in the group used to construct the model (82% in the validation group). Using the low cutoff score of –1.455, advanced fibrosis could be excluded with a negative predictive value of 93% in the construction group and 88% in the validation group.²⁸ A score between the cutoff values merits liver biopsy to determine fibrosis stage. The score is more accurate in patients with diabetes.²⁹ When used by primary care physicians, the NAFLD fibrosis score is more cost-effective than transient elastography and liver biopsy for accurately predicting advanced fibrosis.³⁰

AST-to-platelet ratio index score for HCV, NAFLD

The AST-to-platelet ratio index (APRI) score was developed in 2003 using a cohort of 270 patients with HCV and liver biopsy as the standard. A cutoff value of less than or equal to 0.5 had a negative predictive value of 86% for the absence of significant fibrosis, while a score of more than 1.5 detected the presence of significant fibrosis with a positive predictive value of 88%.³¹ The APRI score was subsequently validated for NAFLD.^27,32

FibroSure uses a patented formula

FibroSure (LabCorp; labcorp.com) uses a patented mathematical formula that takes into account age, sex, and levels of gamma-glutamyl transferase, total bilirubin, haptoglobin, apolipoprotein-A, and alpha-2 macroglobulin to assess fibrosis. Developed in 2001 for use in patients with HCV infection, it was reported to have a positive predictive value of greater than 90% and a negative predictive value of 100% for clinically significant fibrosis, defined as stage 2 to 4 based on the METAVIR staging system in the prediction model.³³ The use of FibroSure in patients with HCV was subsequently validated in various meta-analyses and systematic reviews.^34,35 It is less accurate in patients with normal ALT levels.³⁶

FibroSure also has good accuracy for predicting fibrosis stage in chronic liver disease due to other causes, including NAFLD.³⁷

The prediction models discussed above use routine laboratory tests for chronic liver disease and thus are inexpensive. The high cost of additional testing needed for FibroSure, coupled with the risk of misdiagnosis, makes its cost-effectiveness questionable.³⁸

 

 

IMAGING TO PREDICT FIBROSIS STAGE

Conventional ultrasonography (with or without vascular imaging) and computed tomography can detect cirrhosis on the basis of certain imaging characteristics,^39,40 including the nodular contour of the liver, caudate lobe hypertrophy, ascites, reversal of blood flow in the portal vein, and splenomegaly. However, they cannot detect fibrosis in its early stages.

The 3 methods discussed below provide more accurate fibrosis staging by measuring the velocity of shear waves sent across hepatic tissue. Because shear-wave velocity increases with liver stiffness, the fibrosis stage can be estimated from this information.⁴¹

Transient elastography

Transient elastography uses a special ultrasound transducer. It is highly accurate for predicting advanced fibrosis for almost all causes of chronic liver disease, including HCV infection^42,43 and NAFLD.⁴⁴ The cutoff values of wave velocity to estimate fibrosis stage differ by liver disease etiology.

Transient elastography should not be used to evaluate fibrosis in patients with acute hepatitis, which transiently increases liver stiffness, resulting in a falsely high fibrosis stage diagnosis.⁴⁵ It is also not a good method for evaluating fibrosis in patients with biliary obstruction or extrahepatic venous congestion. Because liver stiffness can increase after eating,⁴⁶ the test should be done under fasting conditions.

A significant limitation of transient elastography has been its poor accuracy in patients with obesity.⁴⁷ This has been largely overcome with the use of a more powerful (XL) probe but is still a limitation for those with morbid obesity.⁴⁸ Because many patients with NAFLD are obese, this limitation can be significant.

Transient elastography has gained popularity for evaluating fibrosis in patients with chronic liver disease for multiple reasons: it is cost-effective and results are highly reproducible, with low variation in results among different observers and in individual observers.⁴⁹ Combined with a platelet count, it can also be used to detect the development of clinically significant portal hypertension in patients with cirrhosis, thus determining the need to screen for esophageal varices using endoscopy.⁵⁰ Screening endoscopy can be avoided in patients whose liver stiffness remains below 20 kPa or whose platelet count is above 150 × 10⁹/L.

Acoustic radiation force imaging

Unlike transient elastography, which requires a separate transducer probe to assess shear- wave velocity, acoustic radiation force imaging uses the same transducer for both this function and imaging. Different image modes are available when testing for liver stiffness, so a region of interest that is optimal for avoiding vascular structures or masses can be selected, increasing accuracy.⁵¹

Acoustic radiation force imaging has been tested in different causes of chronic liver disease, including HCV and NAFLD,⁵² with accuracy similar to that of transient elastography.⁵³ For overweight and obese patients, acoustic radiation force imaging is more accurate than transient elastography using the XL probe.⁵⁴ However, this method is still new, and we need more data to support using one method over the other.

Magnetic resonance elastography

Magnetic resonance elastography uses a special transducer placed under the rib cage to transmit shear waves concurrently with magnetic resonance imaging. It has been tested in patients with HCV and NAFLD and has been found to have better diagnostic accuracy than transient elastography and acoustic radiation force imaging.^55,56 Patients must be fasting for better diagnostic accuracy⁵⁷ and must hold their breath while elastography is performed. The need for breath-holding and the high cost limit the use of this method for assessing fibrosis.

BOTTOM LINE FOR ASSESSING FIBROSIS

Although liver biopsy remains the gold standard for accurately determining fibrosis stage, noninvasive methods, especially imaging techniques, are fast evolving. Guidelines recommend using transient elastography to determine fibrosis stage noninvasively in patients with HCV,⁵⁸ but a similar recommendation cannot be made for NAFLD with available data. For NAFLD, combined elastography and NAFLD fibrosis score are recommended to determine the need for a liver biopsy (Figure 2).⁵⁹ Currently, we recommend using a combination of the scores discussed above and the imaging tests.

Staging of liver fibrosis, important for determining prognosis in patients with chronic liver disease and for the need to start screening for complications of cirrhosis, was traditionally done only by liver biopsy. While biopsy is still the gold standard method to stage fibrosis, noninvasive methods have been developed that can also assess disease severity.

This article briefly reviews the epidemiology and physiology of chronic liver disease and the traditional role of liver biopsy. Pros and cons of alternative fibrosis assessment methods are discussed, with a focus on their utility for patients with nonalcoholic fatty liver disease (NAFLD) and hepatitis C virus (HCV) infection.

CHRONIC LIVER DISEASE: A HUGE HEALTH BURDEN

Chronic liver disease is associated with enormous health and financial costs in the United States. Its prevalence is about 15%,¹ and it is the 12th leading cause of death.² Hospital costs are estimated at about $4 billion annually.³

The most common causes of chronic liver disease are NAFLD (which may be present in up to one-third of the US population and is increasing with the epidemic of obesity), its aggressive variant, nonalcoholic steatohepatitis (NASH) (present in about 3% of the population), and HCV infection (1%).^4,5

Since direct-acting antiviral agents were introduced, HCV infection dropped from being the leading cause of liver transplant to third place.⁶ But at the same time, the number of patients on the transplant waiting list who have NASH has risen faster than for any other cause of chronic liver disease.⁷

FIBROSIS: A KEY INDICATOR OF DISEASE SEVERITY

With any form of liver disease, collagen is deposited in hepatic lobules over time, a process called fibrosis. Both HCV infection and NASH involve necroinflammation in the liver, hepatocyte apoptosis, and activation of stellate cells, leading to progressive collagen deposition in hepatic lobules. Fibrosis typically starts in the region of the central vein and portal tracts and eventually extends to other areas of the lobule.

Determining fibrosis severity is critical when a patient is diagnosed with chronic liver disease, as it predicts long-term clinical outcomes and death in HCV⁸ and NAFLD.⁹ Different staging systems have been developed to reflect the degree of fibrosis, based on its distribution as seen on liver biopsy (Table 1, Figure 1).

In HCV infection, advanced fibrosis is defined as either stage 4 to 6 using the Ishak system¹⁰ or stage 3 to 4 using the Meta-analysis of Histological Data in Viral Hepatitis (METAVIR) system.¹¹

In NAFLD, advanced fibrosis is defined as stage 3 to 4 using the NASH Clinical Research Network system.¹²

Staging fibrosis is also important so that patients with cirrhosis can be identified early to begin screening for hepatocellular carcinoma and esophageal varices to reduce the risks of illness and death. In addition, insurance companies often require documentation of fibrosis stage before treating HCV with the new direct-acting antiviral agents.

LIVER BIOPSY IS STILL THE GOLD STANDARD

Although invasive, liver biopsy remains the gold standard for determining fibrosis stage. Liver biopsies were performed “blindly” (without imaging) until the 1990s, but imaging-guided biopsy using ultrasonography was then developed, which entailed less pain and lower complication and hospitalization rates. Slightly more hepatic tissue is obtained with guided liver biopsy, but the difference was deemed clinically insignificant.¹³ Concern initially arose about the added cost involved with imaging, but imaging-guided biopsy was actually found to be more cost-effective.¹⁴

In the 2000s, transjugular liver biopsy via the right internal jugular vein became available. This method was originally used primarily in patients with ascites or significant coagulopathy. At first, there were concerns about the adequacy of specimens obtained to make an accurate diagnosis or establish fibrosis stage, but this limitation was overcome with improved techniques.^15,16 Transjugular liver biopsy has the additional advantage of enabling one to measure the hepatic venous pressure gradient, which also has prognostic significance; a gradient greater than 10 mm Hg is associated with worse prognosis.¹⁷

Disadvantages of biopsy: Complications, sampling errors

Liver biopsy has disadvantages. Reported rates of complications necessitating hospitalization using the blind method were as high as 6% in the 1970s,¹⁸ dropping to 3.2% in a 1993 study.¹⁹ Bleeding remains the most worrisome complication. With the transjugular method, major and minor complication rates are less than 1% and 7%, respectively.^15,16 Complication rates with imaging-guided biopsy are also low.

Liver biopsy is also prone to sampling error. The number of portal tracts obtained in the biopsy correlates with the accuracy of fibrosis staging, and smaller samples may lead to underestimating fibrosis stage. In patients with HCV, samples more than 15 mm long led to accurate staging diagnosis in 65% of patients, and those longer than 25 mm conferred 75% accuracy.²⁰ Also, different stages can be diagnosed from samples obtained from separate locations in the liver, although rarely is the difference more than a single stage.²¹

Histologic evaluation of liver biopsies is operator-dependent. Although significant interobserver variation has been reported for degree of inflammation, there tends to be good concordance for fibrosis staging.^22,23

 

 

STAGING BASED ON DEMOGRAPHIC AND LABORATORY VARIABLES

Several scores based on patient characteristics and laboratory values have been developed for assessing liver fibrosis and have been specifically validated for HCV infection, NAFLD, or both. They can serve as inexpensive initial screening tests for the presence or absence of advanced fibrosis.

FIB-4 index for HCV, NAFLD

The FIB-4 index predicts the presence of advanced fibrosis using, as its name indicates, a combination of 4 factors in fibrosis: age, platelet count, and the levels of aspartate aminotransferase (AST) and alanine aminotransferase (ALT), according to the formula:

FIB-4 index = (age × AST [U/L]) /
(platelet count [× 10⁹/L] × √ALT [U/L]).

The index was derived from data from 832 patients co-infected with HCV and human immunodeficiency virus.²⁴ The Ishak staging system¹⁰ for fibrosis on liver biopsy was used for confirmation, with stage 4 to 6 defined as advanced fibrosis. A cutoff value of more than 3.25 had a positive predictive value of 65% for advanced fibrosis, and to exclude advanced fibrosis, a cutoff value of less than 1.45 had a negative predictive value of 90%.

The FIB-4 index has since been validated in patients with HCV infection²⁵ and NAFLD.²⁶ In a subsequent study in 142 patients with NAFLD, the FIB-4 index was more accurate in diagnosing advanced fibrosis than the other noninvasive prediction models discussed below.²⁷

NAFLD fibrosis score

The NAFLD fibrosis score, constructed and validated only in patients with biopsy-confirmed NAFLD, incorporates age, body mass index, presence of diabetes or prediabetes, albumin level, platelet count, and AST and ALT levels.

A group of 480 patients was used to construct the score, and 253 patients were used to validate it. Using the high cutoff value of 0.676, the presence of advanced fibrosis was diagnosed with a positive predictive value of 90% in the group used to construct the model (82% in the validation group). Using the low cutoff score of –1.455, advanced fibrosis could be excluded with a negative predictive value of 93% in the construction group and 88% in the validation group.²⁸ A score between the cutoff values merits liver biopsy to determine fibrosis stage. The score is more accurate in patients with diabetes.²⁹ When used by primary care physicians, the NAFLD fibrosis score is more cost-effective than transient elastography and liver biopsy for accurately predicting advanced fibrosis.³⁰

AST-to-platelet ratio index score for HCV, NAFLD

The AST-to-platelet ratio index (APRI) score was developed in 2003 using a cohort of 270 patients with HCV and liver biopsy as the standard. A cutoff value of less than or equal to 0.5 had a negative predictive value of 86% for the absence of significant fibrosis, while a score of more than 1.5 detected the presence of significant fibrosis with a positive predictive value of 88%.³¹ The APRI score was subsequently validated for NAFLD.^27,32

FibroSure uses a patented formula

FibroSure (LabCorp; labcorp.com) uses a patented mathematical formula that takes into account age, sex, and levels of gamma-glutamyl transferase, total bilirubin, haptoglobin, apolipoprotein-A, and alpha-2 macroglobulin to assess fibrosis. Developed in 2001 for use in patients with HCV infection, it was reported to have a positive predictive value of greater than 90% and a negative predictive value of 100% for clinically significant fibrosis, defined as stage 2 to 4 based on the METAVIR staging system in the prediction model.³³ The use of FibroSure in patients with HCV was subsequently validated in various meta-analyses and systematic reviews.^34,35 It is less accurate in patients with normal ALT levels.³⁶

FibroSure also has good accuracy for predicting fibrosis stage in chronic liver disease due to other causes, including NAFLD.³⁷

The prediction models discussed above use routine laboratory tests for chronic liver disease and thus are inexpensive. The high cost of additional testing needed for FibroSure, coupled with the risk of misdiagnosis, makes its cost-effectiveness questionable.³⁸

 

 

IMAGING TO PREDICT FIBROSIS STAGE

Conventional ultrasonography (with or without vascular imaging) and computed tomography can detect cirrhosis on the basis of certain imaging characteristics,^39,40 including the nodular contour of the liver, caudate lobe hypertrophy, ascites, reversal of blood flow in the portal vein, and splenomegaly. However, they cannot detect fibrosis in its early stages.

The 3 methods discussed below provide more accurate fibrosis staging by measuring the velocity of shear waves sent across hepatic tissue. Because shear-wave velocity increases with liver stiffness, the fibrosis stage can be estimated from this information.⁴¹

Transient elastography

Transient elastography uses a special ultrasound transducer. It is highly accurate for predicting advanced fibrosis for almost all causes of chronic liver disease, including HCV infection^42,43 and NAFLD.⁴⁴ The cutoff values of wave velocity to estimate fibrosis stage differ by liver disease etiology.

Transient elastography should not be used to evaluate fibrosis in patients with acute hepatitis, which transiently increases liver stiffness, resulting in a falsely high fibrosis stage diagnosis.⁴⁵ It is also not a good method for evaluating fibrosis in patients with biliary obstruction or extrahepatic venous congestion. Because liver stiffness can increase after eating,⁴⁶ the test should be done under fasting conditions.

A significant limitation of transient elastography has been its poor accuracy in patients with obesity.⁴⁷ This has been largely overcome with the use of a more powerful (XL) probe but is still a limitation for those with morbid obesity.⁴⁸ Because many patients with NAFLD are obese, this limitation can be significant.

Transient elastography has gained popularity for evaluating fibrosis in patients with chronic liver disease for multiple reasons: it is cost-effective and results are highly reproducible, with low variation in results among different observers and in individual observers.⁴⁹ Combined with a platelet count, it can also be used to detect the development of clinically significant portal hypertension in patients with cirrhosis, thus determining the need to screen for esophageal varices using endoscopy.⁵⁰ Screening endoscopy can be avoided in patients whose liver stiffness remains below 20 kPa or whose platelet count is above 150 × 10⁹/L.

Acoustic radiation force imaging

Unlike transient elastography, which requires a separate transducer probe to assess shear- wave velocity, acoustic radiation force imaging uses the same transducer for both this function and imaging. Different image modes are available when testing for liver stiffness, so a region of interest that is optimal for avoiding vascular structures or masses can be selected, increasing accuracy.⁵¹

Acoustic radiation force imaging has been tested in different causes of chronic liver disease, including HCV and NAFLD,⁵² with accuracy similar to that of transient elastography.⁵³ For overweight and obese patients, acoustic radiation force imaging is more accurate than transient elastography using the XL probe.⁵⁴ However, this method is still new, and we need more data to support using one method over the other.

Magnetic resonance elastography

Magnetic resonance elastography uses a special transducer placed under the rib cage to transmit shear waves concurrently with magnetic resonance imaging. It has been tested in patients with HCV and NAFLD and has been found to have better diagnostic accuracy than transient elastography and acoustic radiation force imaging.^55,56 Patients must be fasting for better diagnostic accuracy⁵⁷ and must hold their breath while elastography is performed. The need for breath-holding and the high cost limit the use of this method for assessing fibrosis.

BOTTOM LINE FOR ASSESSING FIBROSIS

Although liver biopsy remains the gold standard for accurately determining fibrosis stage, noninvasive methods, especially imaging techniques, are fast evolving. Guidelines recommend using transient elastography to determine fibrosis stage noninvasively in patients with HCV,⁵⁸ but a similar recommendation cannot be made for NAFLD with available data. For NAFLD, combined elastography and NAFLD fibrosis score are recommended to determine the need for a liver biopsy (Figure 2).⁵⁹ Currently, we recommend using a combination of the scores discussed above and the imaging tests.

Laboratory tests are often ordered inappropriately for patients in whom a rheumatologic illness is suspected; this occurs in both primary and secondary care.¹ Some tests are available both singly and as part of a battery of tests screening healthy people without symptoms.

The problem: negative test results are by no means always reassuring, and false-positive results raise the risks of unnecessary anxiety for patients and clinicians, needless referrals, and potential morbidity due to further unnecessary testing and exposure to wrong treatments.² Clinicians should be aware of the pitfalls of these tests in order to choose them wisely and interpret the results correctly.

This article provides practical guidance on requesting and interpreting some common tests in rheumatology, with the aid of case vignettes.

RHEUMATOID FACTOR AND ANTICITRULLINATED PEPTIDE ANTIBODY

A 41-year-old woman, previously in good health, presents to her primary care practitioner with a 6-week history of pain and swelling in her hands and early morning stiffness lasting about 2 hours. She denies having any extraarticular symptoms. Physical examination reveals synovitis across her right metacarpophalangeal joints, proximal interphalangeal joint of the left middle finger, and left wrist. The primary care physician is concerned that her symptoms might be due to rheumatoid arthritis.

Would testing for rheumatoid factor and anticitrullinated peptide antibody be useful in this patient?

Rheumatoid factor is an antibody (immunoglobulin M, IgG, or IgA) targeted against the Fc fragment of IgG.³ It was so named because it was originally detected in patients with rheumatoid arthritis, but it is neither sensitive nor specific for this condition. A meta-analysis of more than 5,000 patients with rheumatoid arthritis reported that rheumatoid factor testing had a sensitivity of 69% and specificity of 85%.⁴

Numerous other conditions can be associated with a positive test for rheumatoid factor (Table 1). Hence, a diagnosis of rheumatoid arthritis cannot be confirmed with a positive result alone, nor can it be excluded with a negative result.

Anticitrullinated peptide antibody, on the other hand, is much more specific for rheumatoid arthritis (95%), as it is seldom seen in other conditions, but its sensitivity is similar to that of rheumatoid factor (68%).^4–6 A positive result would thus lend strength to the diagnosis of rheumatoid arthritis, but a negative result would not exclude it.

Approach to early arthritis

When faced with a patient with early arthritis, some key questions to ask include^7,8:

Is this an inflammatory or a mechanical problem? Inflammatory arthritis is suggested by joint swelling that is not due to trauma or bony hypertrophy, early morning stiffness lasting longer than 30 minutes, and elevated inflammatory markers (erythrocyte sedimentation rate or C-reactive protein). Involvement of the small joints of the hands and feet may be suggested by pain on compression of the metacarpophalangeal and metatarsophalangeal joints, respectively.

Is there a definite identifiable underlying cause for the inflammatory arthritis? The pattern of development of joint symptoms or the presence of extraarticular symptoms may suggest an underlying problem such as gout, psoriatic arthritis, systemic lupus erythematosus, or sarcoidosis.

If the arthritis is undifferentiated (ie, there is no definite identifiable cause), is it likely to remit or persist? This is perhaps the most important question to ask in order to prognosticate. Patients with risk factors for persistent disease, ie, for development of rheumatoid arthritis, should be referred to a rheumatologist early for timely institution of disease-modifying antirheumatic drug therapy.⁹ Multiple studies have shown that patients in whom this therapy is started early have much better clinical, functional, and radiologic outcomes than those in whom it is delayed.^10–12

The revised American College of Rheumatology and European League Against Rheumatism criteria¹³ include the following factors as predictors of persistence:

• Number of involved joints (with greater weight given to involvement of small joints)
• Duration of symptoms 6 weeks or longer
• Elevated acute-phase response (erythrocyte sedimentation rate or C-reactive protein level)
• A positive serologic test (either rheumatoid factor or anticitrullinated peptide antibody).

If both rheumatoid factor and anticitrullinated peptide antibody are positive in a patient with early undifferentiated arthritis, the risk of progression to rheumatoid arthritis is almost 100%, thus underscoring the importance of testing for these antibodies.^5,6 Referral to a rheumatologist should, however, not be delayed in patients with negative test results (more than one-third of patients with rheumatoid arthritis may be negative for both), and should be considered in those with inflammatory joint symptoms persisting longer than 6 weeks, especially with involvement of the small joints (sparing the distal interphalangeals) and elevated acute-phase response.

Rheumatoid factor in healthy people without symptoms

In some countries, testing for rheumatoid factor is offered as part of a battery of screening tests in healthy people who have no symptoms, a practice that should be strongly discouraged.

Multiple studies, both prospective and retrospective, have demonstrated that both rheumatoid factor and anticitrullinated peptide antibody may be present several years before the clinical diagnosis of rheumatoid arthritis.^6,14–16 But the risk of developing rheumatoid arthritis for asymptomatic individuals who are rheumatoid factor-positive depends on the rheumatoid factor titer, positive family history of rheumatoid arthritis in first-degree relatives, and copresence of anticitrullinated peptide antibody. The absolute risk, nevertheless, is still very small. In some, there might be an alternative explanation such as undiagnosed Sjögren syndrome or hepatitis C.

In any event, no strategy is currently available that is proven to prevent the development of rheumatoid arthritis, and there is no role for disease-modifying therapy during the preclinical phase.¹⁶

Back to our patient

Blood testing in our patient reveals normal complete blood cell counts, aminotransferase levels, and serum creatinine concentration; findings on urinalysis are normal. Her erythrocyte sedimentation rate is 56 mm/hour (reference range 0–15), and her C-reactive protein level is 26 mg/dL (normal < 3). Testing is negative for rheumatoid factor and anticitrullinated peptide antibody.

Although her rheumatoid factor and anticitrullinated peptide antibody tests are negative, she is referred to a rheumatologist because she has predictors of persistent disease, ie, symptom duration of 6 weeks, involvement of the small joints of the hands, and elevated erythrocyte sedimentation rate and C-reactive protein. The rheumatologist checks her parvovirus serology, which is negative.

The patient is given parenteral depot corticosteroid therapy, to which she responds briefly. Because her symptoms persist and continue to worsen, methotrexate treatment is started after an additional 6 weeks.

 

 

ANTINUCLEAR ANTIBODY

A 37-year-old woman presents to her primary care physician with the complaint of tiredness. She has a family history of systemic lupus erythematosus in her sister and maternal aunt. She is understandably worried about lupus because of the family history and is asking to be tested for it.

Would testing for antinuclear antibody be reasonable?

Antinuclear antibody is not a single antibody but rather a family of autoantibodies that are directed against nuclear constituents such as single- or double-stranded deoxyribonucleic acid (dsDNA), histones, centromeres, proteins complexed with ribonucleic acid (RNA), and enzymes such as topoisomerase.^17,18

Protein antigens complexed with RNA and some enzymes in the nucleus are also known as extractable nuclear antigens (ENAs). They include Ro, La, Sm, Jo-1, RNP, and ScL-70 and are named after the patient in whom they were first discovered (Robert, Lavine, Smith, and John), the antigen that is targeted (ribonucleoprotein or RNP), and the disease with which they are associated (anti-ScL-70 or antitopoisomerase in diffuse cutaneous scleroderma).

Antinuclear antibody testing is commonly requested to exclude connective tissue diseases such as lupus, but the clinician needs to be aware of the following points:

Antinuclear antibody may be encountered in conditions other than lupus

These include¹⁹:

• Other autoimmune diseases such as rheumatoid arthritis, primary Sjögren syndrome, systemic sclerosis, autoimmune thyroid disease, and myasthenia gravis
• Infection with organisms that share the epitope with self-antigens (molecular mimicry)
• Cancers
• Drugs such as hydralazine, procainamide, and minocycline.

Antinuclear antibody might also be produced by the healthy immune system from time to time to clear the nuclear debris that is extruded from aging cells.

A study in healthy individuals²⁰ reported a prevalence of positive antinuclear antibody of 32% at a titer of 1/40, 15% at a titer of 1/80, 7% at a titer of 1/160, and 3% at a titer of 1/320. Importantly, a positive result was more common among family members of patients with autoimmune connective tissue diseases.²¹ Hence, a positive antinuclear antibody result does not always mean lupus.

Antinuclear antibody testing is highly sensitive for lupus

With current laboratory methods, antinuclear antibody testing has a sensitivity close to 100%. Hence, a negative result virtually rules out lupus.

Two methods are commonly used to test for antinuclear antibody: indirect immunofluorescence and enzyme-linked immunosorbent assay (ELISA).²² While human epithelial (Hep2) cells are used as the source of antigen in immunofluorescence, purified nuclear antigens coated on multiple-well plates are used in ELISA.

Although ELISA is simpler to perform, immunofluorescence has a slightly better sensitivity (because the Hep2 cells express a wide range of antigens) and is still considered the gold standard. As expected, the higher sensitivity occurs at the cost of reduced specificity (about 60%), so antinuclear antibody will also be detected in all the other conditions listed above.²³

To improve the specificity of antinuclear antibody testing, laboratories report titers (the highest dilution of the test serum that tested positive); a cutoff of greater than 1/80 is generally considered significant.

Do not order antinuclear antibody testing indiscriminately

If the antinuclear antibody test is requested indiscriminately, the positive predictive value for the diagnosis of lupus is only 11%.²⁴ The test should be requested only when the pretest probability of lupus or other connective tissue disease is high. The positive predictive value is much higher in patients presenting with clinical or laboratory manifestations involving 2 or more organ systems (Table 2).^18,25

Categorization of the specific antigen target improves disease specificity. The antinuclear antibody in patients with lupus may be targeted against single- or double-stranded DNA, histones, or 1 or more of the ENAs. Among these, the presence of anti-dsDNA or anti-Sm is highly specific for a diagnosis of lupus (close to 100%). Neither is sensitive for lupus, however, with anti-dsDNA present in only 60% of patients with lupus and anti-Sm in about 30%.¹⁷ Hence, patients with a positive antinuclear antibody and negative anti-dsDNA and anti-Sm may continue to pose a diagnostic challenge. Other examples of specific disease associations are listed in Table 3.

To sum up, the antinuclear antibody test should be requested only in patients with involvement of multiple organ systems. Although a negative result would make it extremely unlikely that the clinical presentation is due to lupus, a positive result is insufficient on its own to make a diagnosis of lupus.

Diagnosing lupus is straightforward when patients present with a specific manifestation such as inflammatory arthritis, photosensitive skin rash, hemolytic anemia, thrombocytopenia, or nephritis, or with specific antibodies such as those against dsDNA or Sm. Patients who present with nonspecific symptoms such as arthralgia or tiredness with a positive antinuclear antibody and negative anti-dsDNA and anti-Sm may present difficulties even for the specialist.^25–27

Back to our patient

Our patient denies arthralgia. She has no extraarticular symptoms such as skin rashes, oral ulcers, sicca symptoms, muscle weakness, Raynaud phenomenon, pleuritic chest pain, or breathlessness. Findings on physical examination and urinalysis are unremarkable.

Her primary care physician decides to check her complete blood cell count, erythrocyte sedimentation rate, and thyroid-stimulating hormone level. Although she is reassured that her tiredness is not due to lupus, she insists on getting an antinuclear antibody test.

Her complete blood cell counts are normal. Her erythrocyte sedimentation rate is 6 mm/hour. However, her thyroid-stimulating hormone level is elevated, and subsequent testing shows low free thyroxine and positive thyroid peroxidase antibodies. The antinuclear antibody is positive in a titer of 1/80 and negative for anti-dsDNA and anti-ENA.

We explain to her that the positive antinuclear antibody is most likely related to her autoimmune thyroid disease. She is referred to an endocrinologist.

 

 

ANTIPHOSPHOLIPID ANTIBODIES

A 24-year-old woman presents to the emergency department with acute unprovoked deep vein thrombosis in her right leg, confirmed by ultrasonography. She has no history of previous thrombosis, and the relevant family history is unremarkable. She has never been pregnant. Her platelet count is 84 × 10⁹/L (reference range 150–400), and her baseline activated partial thromboplastin time is prolonged at 62 seconds (reference range 23.0–32.4). The rest of her blood counts and her prothrombin time, liver enzyme levels, and serum creatinine level are normal.

Should this patient be tested for antiphospholipid antibodies?

Antiphospholipid antibodies are important because of their association with thrombotic risk (both venous and arterial) and pregnancy morbidity. The name is a misnomer, as these antibodies are targeted against some proteins that are bound to phospholipids and not only to the phospholipids themselves.

According to the modified Sapporo criteria for the classification of antiphospholipid syndrome,²⁸ antiphospholipid antibodies should remain persistently positive on at least 2 separate occasions at least 12 weeks apart for the result to be considered significant because some infections and drugs may be associated with the transient presence of antiphospholipid antibodies.

Screening for antiphospholipid antibodies should include testing for IgM and IgG anticardiolipin antibodies, lupus anticoagulant, and IgM and IgG beta-2 glycoprotein I antibodies.^29,30

Anticardiolipin antibodies

Anticardiolipin (aCL) antibodies may be targeted either against beta-2 glycoprotein I (beta-2GPI) that is bound to cardiolipin (a phospholipid) or against cardiolipin alone; the former is more specific. Antibodies directed against cardiolipin alone are usually transient and are associated with infections and drugs. The result is considered significant only when anticardiolipin antibodies are present in a medium to high titer (> 40 IgG phospholipid units or IgM phospholipid units, or > 99th percentile).

Lupus anticoagulant

The antibody with “lupus anticoagulant activity” is targeted against prothrombin plus phospholipid or beta-2GPI plus phospholipid. The test for it is a functional assay involving 3 steps:

Demonstrating the prolongation of a phospholipid-dependent coagulation assay like the activated partial thromboplastin time (aPTT). (This may explain the prolongation of aPTT in the patient described in the vignette.) Although the presence of lupus anticoagulant is associated with thrombosis, it is called an “anticoagulant” because of this in vitro prolongation of phospholipid-dependent coagulation assays.

Mixing study. The phospholipid-dependent coagulation assay could be prolonged because of either the deficiency of a coagulation factor or the presence of the antiphospholipid antibodies. This can be differentiated by mixing the patient’s plasma with normal plasma (which will have all the clotting factors) in a 1:1 ratio. If the coagulation assay remains prolonged after the addition of normal plasma, clotting factor deficiency can be excluded.

Addition of a phospholipid. If the prolongation of the coagulation assay is due to the presence of an antiphospholipid antibody, addition of extra phospholipid will correct this.

Beta-2 glycoprotein I antibody (anti-beta-2GPI)

The beta-2GPI that is not bound to the cardiolipin can be detected by separately testing for beta-2GPI (the anticardiolipin test only detects the beta-2GPI that is bound to the cardiolipin). The result is considered significant if beta-2GPI is present in a medium to high titer (> 99th percentile).

Studies have shown that antiphospholipid antibodies may be present in 1% to 5% of apparently healthy people in the general population.³¹ These are usually low-titer anticardiolipin or anti-beta-GPI IgM antibodies that are not associated with thrombosis or adverse pregnancy outcomes. Hence, the term antiphospholipid syndrome should be reserved for those who have had at least 1 episode of thrombosis or pregnancy morbidity and persistent antiphospholipid antibodies, and not those who have asymptomatic or transient antiphospholipid antibodies.

Triple positivity (positive anticardiolipin, lupus anticoagulant, and anti-beta-2GPI) seems to be associated with the highest risk of thrombosis, with a 10-year cumulative incidence of 37.1% (95% confidence interval [CI] 19.9–54.3) for a first thrombotic event,³² and 44.2% (95% CI 38.6–49.8) for recurrent thrombosis.³³

The association with thrombosis is stronger for lupus anticoagulant than with the other 2 antibodies, with different studies³⁴ finding an odds ratio ranging from 5 to 16. A positive lupus anticoagulant test with or without a moderate to high titer of anticardiolipin or anti-beta-2GPI IgM or IgG constitutes a high-risk profile, while a moderate to high titer of anticardiolipin or anti-beta-2GPI IgM or IgG constitutes a moderate-risk profile. A low titer of anticardiolipin or anti-beta-2GPI IgM or IgG constitutes a low-risk profile that may not be associated with thrombosis.³⁵

Antiphospholipid syndrome is important to recognize because of the need for long-term anticoagulation to prevent recurrence.³⁶ It may be primary, when it occurs on its own, or secondary, when it occurs in association with another autoimmune disease such as lupus.

Venous events in antiphospholipid syndrome most commonly manifest as lower-limb deep vein thrombosis or pulmonary embolism, while arterial events most commonly manifest as stroke or transient ischemic attack.³⁷ Obstetric manifestations may include not only miscarriage and stillbirth, but also preterm delivery, intrauterine growth retardation, and preeclampsia, all occurring due to placental insufficiency.

The frequency of antiphospholipid antibodies has been estimated as 13.5% in patients with stroke, 11% with myocardial infarction, 9.5% with deep vein thrombosis, and 6% for those with pregnancy morbidity.³⁸

Some noncriteria manifestations have also been recognized in antiphospholipid syndrome, such as thrombocytopenia, cardiac vegetations (Libman-Sachs endocarditis), livedo reticularis, and nephropathy.

The indications for antiphospholipid antibody testing are listed in Table 4.²⁹ For the patient described in the vignette, it would be appropriate to test for antiphospholipid antibodies because of her unprovoked thrombosis, thrombocytopenia, and prolonged aPTT. Anticoagulant treatment is known to be associated with false-positive lupus anticoagulant, so any blood samples should be drawn before such treatment is commenced.

Back to our patient

Our patient’s anticardiolipin IgG test is negative, while her lupus anticoagulant and beta-2GPI IgG are positive. She has no clinical or laboratory features suggesting lupus.

She is started on warfarin. After 3 months, the warfarin is interrupted for several days, and she is retested for all 3 antiphospholipid antibodies. Her beta-2GPI I IgG and lupus anticoagulant tests are again positive. Because of the persistent antiphospholipid antibody positivity and clinical history of deep vein thrombosis, her condition is diagnosed as primary antiphospholipid syndrome. She is advised to continue anticoagulant therapy indefinitely.

 

 

ANTINEUTROPHIL CYTOPLASMIC ANTIBODY

A 34-year-old man who is an injecting drug user presents with a 2-week history of fever, malaise, and generalized arthralgia. There are no localizing symptoms of infection. Notable findings on examination include a temperature of 38.0°C (100.4°F), needle track marks in his arms, nonblanching vasculitic rash in his legs, and a systolic murmur over the precordium.

His white blood cell count is 15.3 × 10⁹/L (reference range 3.7–11.0), and his C-reactive protein level is 234 mg/dL (normal < 3). Otherwise, results of blood cell counts, liver enzyme tests, renal function tests, urinalysis, and chest radiography are normal.

Two sets of blood cultures are drawn. Transthoracic echocardiography and the antineutrophil cytoplasmic antibody (ANCA) test are requested, as are screening tests for human immunodeficiency virus, hepatitis B, and hepatitis C.

Was the ANCA test indicated in this patient?

ANCAs are autoantibodies against antigens located in the cytoplasmic granules of neutrophils and monocytes. They are associated with small-vessel vasculitides such as granulomatosis with polyangiitis (GPA), microscopic polyangiitis (MPA), eosinophilic granulomatosis with polyangiitis (EGPA), and isolated pauciimmune crescentic glomerulonephritis, all collectively known as ANCA-associated vasculitis (AAV).³⁹

Laboratory methods to detect ANCA include indirect immunofluorescence and antigen-specific enzyme immunoassays. Indirect immunofluorescence only tells us whether or not an antibody that is targeting a cytoplasmic antigen is present. Based on the indirect immunofluorescent pattern, ANCA can be classified as follows:

• Perinuclear or p-ANCA (if the targeted antigen is located just around the nucleus and extends into it)
• Cytoplasmic or c-ANCA (if the targeted antigen is located farther away from the nucleus)
• Atypical ANCA (if the indirect immunofluorescent pattern does not fit with either p-ANCA or c-ANCA).

Indirect immunofluorescence does not give information about the exact antigen that is targeted; this can only be obtained by performing 1 of the antigen-specific immunoassays. The target antigen for c-ANCA is usually proteinase-3 (PR3), while that for p-ANCA could be myeloperoxidase (MPO), cathepsin, lysozyme, lactoferrin, or bactericidal permeability inhibitor. Anti-PR3 is highly specific for GPA, while anti-MPO is usually associated with MPA and EGPA. Less commonly, anti-PR3 may be seen in patients with MPA and anti-MPO in those with GPA. Hence, there is an increasing trend toward classifying ANCA-associated vasculitis into PR3-associated or MPO-associated vasculitis rather than as GPA, MPA, EGPA, or renal-limited vasculitis.⁴⁰

Several audits have shown that the ANCA test is widely misused and requested indiscriminately to rule out vasculitis. This results in a lower positive predictive value, possible harm to patients due to increased false-positive rates, and increased burden on the laboratory.^41–43 At least 2 separate groups have demonstrated that a gating policy that refuses ANCA testing in patients without clinical evidence of systemic vasculitis can reduce the number of inappropriate requests, improve the diagnostic yield, and make it more clinically relevant and cost-effective.^44,45

The clinician should bear in mind that:

ANCA testing should be requested only if the pretest probability of ANCA-associated vasculitis is high. The indications proposed by the International Consensus Statement on ANCA testing⁴⁶ are listed in Table 5. These criteria have been clinically validated, with 1 study even demonstrating that no cases of ANCA-associated vasculitis would be missed if these guidelines are followed.⁴⁷

Current guidelines recommend using one of the antigen-specific assays for PR3 and MPO as the primary screening method.⁴⁸ Until recently, indirect immunofluorescence was used to screen for ANCA-associated vasculitis, and positive results were confirmed by ELISA to detect ANCAs specific for PR3 and MPO,⁴⁹ but this is no longer recommended because of recent evidence suggesting a large variability between the different indirect immunofluorescent methods and improved diagnostic performance of the antigen-specific assays.

In a large multicenter study by Damoiseaux et al, the specificity with the different antigen-specific immunoassays was 98% to 99% for PR3-ANCA and 96% to 99% for MPO-ANCA.⁵⁰

ANCA-associated vasculitis should not be considered excluded if the PR3 and MPO-ANCA are negative. In the Damoiseaux study, about 11% to 15% of patients with GPA and 8% to 24% of patients with MPA tested negative for both PR3 and MPO-ANCA.⁵⁰

If the ANCA result is negative and clinical suspicion for ANCA-associated vasculitis is high, the clinician may wish to consider requesting another immunoassay method or indirect immunofluorescence. Results of indirect immunofluorescent testing results may be positive in those with a negative immunoassay, and vice versa.

A positive ANCA result is not diagnostic of ANCA-associated vasculitis. Numerous other conditions are associated with ANCA, usually p-ANCA or atypical ANCA (Table 6). The antigens targeted by these ANCAs are usually cathepsin, lysozyme, lactoferrin, and bactericidal permeability inhibitor.

Thus, the ANCA result should always be interpreted in the context of the whole clinical picture.⁵¹ Biopsy should still be considered the gold standard for the diagnosis of ANCA-associated vasculitis. The ANCA titer can help to improve clinical interpretation, because the likelihood of ANCA-associated vasculitis increases with higher levels of PR3 and MPO-ANCA.⁵²

Back to our patient

Our patient’s blood cultures grow methicillin-sensitive Staphylococcus aureus in both sets after 48 hours. Transthoracic echocardiography reveals vegetations around the tricuspid valve, with no evidence of valvular regurgitation. The diagnosis is right-sided infective endocarditis. He is started on appropriate antibiotics.

Tests for human immunodeficiency virus, hepatitis B, and hepatitis C are negative. The ANCA test is positive for MPO-ANCA at 28 IU/mL (normal < 10).

The positive ANCA is thought to be related to the infective endocarditis. His vasculitis is most likely secondary to infective endocarditis and not ANCA-associated vasculitis. The ANCA test need not have been requested in the first place.

 

 

HUMAN LEUKOCYTE ANTIGEN-B27

A 22-year-old man presents to his primary care physician with a 4-month history of gradually worsening low back pain associated with early morning stiffness lasting more than 2 hours. He has no peripheral joint symptoms.

In the last 2 years, he has had 2 separate episodes of uveitis. There is a family history of ankylosing spondylitis in his father. Examination reveals global restriction of lumbar movements but is otherwise unremarkable. Magnetic resonance imaging (MRI) of the lumbar spine and sacroiliac joints is normal.

Should this patient be tested for human leukocyte antigen-B27 (HLA-B27)?

The major histocompatibility complex (MHC) is a gene complex that is present in all animals. It encodes proteins that help with immunologic tolerance. HLA simply refers to the human version of the MHC.⁵³ The HLA gene complex, located on chromosome 6, is categorized into class I, class II, and class III. HLA-B is one of the 3 class I genes. Thus, a positive HLA-B27 result simply means that the particular gene is present in that person.

HLA-B27 is strongly associated with ankylosing spondylitis, also known as axial spondyloarthropathy.⁵⁴ Other genes also contribute to the pathogenesis of ankylosing spondylitis, but HLA-B27 is present in more than 90% of patients with this disease and is by far considered the most important. The association is not as strong for peripheral spondyloarthropathy, with studies reporting a frequency of up to 75% for reactive arthritis and inflammatory bowel disease-associated arthritis, and up to 50% for psoriatic arthritis and uveitis.⁵⁵

About 9% of healthy, asymptomatic individuals may have HLA-B27, so the mere presence of this gene is not evidence of disease.⁵⁶ There may be up to a 20-fold increased risk of ankylosing spondylitis among those who are HLA-B27-positive.⁵⁷

Some HLA genes have many different alleles, each of which is given a number (explaining the number 27 that follows the B). Closely related alleles that differ from one another by only a few amino-acid substitutions are then categorized together, thus accounting for more than 100 subtypes of HLA-B27 (designated from HLA-B*2701 to HLA-B*27106). These subtypes vary in frequency among different racial groups, and the population prevalence of ankylosing spondylitis parallels the frequency of HLA-B27.⁵⁸ The most common subtype seen in white people and American Indians is B*2705. HLA-B27 is rare in blacks, explaining the rarity of ankylosing spondylitis in this population. Further examples include HLA-B*2704, which is seen in Asians, and HLA-B*2702, seen in Mediterranean populations. Not all subtypes of HLA-B27 are associated with disease, and some, like HLA-B*2706, may also be protective.

When should the clinician consider testing for HLA-B27?

Not all patients with low back pain need an HLA-B27 test. First, it is important to look for clinical features of axial spondyloarthropathy (Table 7). The unifying feature of spondyloarthropathy is enthesitis (inflammation at the sites of insertion of tendons or ligaments on the skeleton). Inflammation of axial entheses causes spondylitis and sacroiliitis, manifesting as inflammatory back pain. Clinical clues to inflammatory back pain include insidious onset, aggravation with rest or inactivity, prolonged early morning stiffness, disturbed sleep during the second half of the night, relief with movement or activity, alternating gluteal pain (due to sacroiliitis), and good response to anti-inflammatory medication (although nonspecific).

Peripheral spondyloarthropathy may present with arthritis, enthesitis (eg, heel pain due to inflammation at the site of insertion of the Achilles tendon or plantar fascia), or dactylitis (“sausage” swelling of the whole finger or toe due to extension of inflammation beyond the margins of the joint). Other clues may include psoriasis, inflammatory bowel disease, history of preceding gastrointestinal or genitourinary infection, family history of similar conditions, and history of recurrent uveitis.

For the initial assessment of patients who have inflammatory back pain, plain radiography of the sacroiliac joints is considered the gold standard.⁵⁹ If plain radiography does not show evidence of sacroiliitis, MRI of the sacroiliac joints should be considered. While plain radiography can reveal only structural changes such as sclerosis, erosions, and ankylosis, MRI is useful to evaluate for early inflammatory changes such as bone marrow edema. Imaging the lumbar spine is not necessary, as the sacroiliac joints are almost invariably involved in axial spondyloarthropathy, and lesions seldom occur in the lumbar spine in isolation.⁶⁰

The diagnosis of ankylosing spondylitis previously relied on confirmatory imaging features, but based on the new International Society classification criteria,^61–63 which can be applied to patients with more than 3 months of back pain and age of onset of symptoms before age 45, patients can be classified as having 1 of the following:

• Radiographic axial spondyloarthropathy, if they have evidence of sacroiliitis on imaging plus 1 other feature of spondyloarthropathy
• Nonradiographic axial spondyloarthropathy, if they have a positive HLA-B27 plus 2 other features of spondyloarthropathy (Table 7).

These new criteria have a sensitivity of 82.9% and specificity of 84.4%.^62,63 The disease burden of radiographic and nonradiographic axial spondyloarthropathy has been shown to be similar, suggesting that they are part of the same disease spectrum. Thus, the HLA-B27 test is useful to make a diagnosis of axial spondyloarthropathy even in the absence of imaging features and could be requested in patients with 2 or more features of spondyloarthropathy. In the absence of imaging features and a negative HLA-B27 result, however, the patient cannot be classified as having axial spondyloarthropathy.

Back to our patient

The absence of radiographic evidence would not exclude axial spondyloarthropathy in our patient. The HLA-B27 test is requested because of the inflammatory back pain and the presence of 2 spondyloarthropathy features (uveitis and the family history) and is reported to be positive. His disease is classified as nonradiographic axial spondyloarthropathy.

He is started on regular naproxen and is referred to a physiotherapist. After 1 month, he reports significant symptomatic improvement. He asks if he can be retested for HLA-B27 to see if it has become negative. We tell him that there is no point in repeating it, as it is a gene and will not disappear.

SUMMARY: CONSIDER THE CLINICAL PICTURE

When approaching a patient suspected of having a rheumatologic disease, a clinician should first consider the clinical presentation and the intended purpose of each test. The tests, in general, might serve several purposes. They might help to:

Increase the likelihood of the diagnosis in question. For example, a positive rheumatoid factor or anticitrullinated peptide antibody can help diagnose rheumatoid arthritis in a patient with early polyarthritis, a positive HLA-B27 can help diagnose ankylosing spondylitis in patients with inflammatory back pain and normal imaging, and a positive ANCA can help diagnose ANCA-associated vasculitis in a patient with glomerulonephritis.

Reduce the likelihood of the diagnosis in question. For example, a negative antinuclear antibody test reduces the likelihood of lupus in a patient with joint pains.

Monitor the condition. For example DNA antibodies can be used to monitor the activity of lupus.

Plan the treatment strategy. For example, one might consider lifelong anticoagulation if antiphospholipid antibodies are persistently positive in a patient with thrombosis.

Prognosticate. For example, positive rheumatoid factor and anticitrullinated peptide antibody increase the risk of erosive rheumatoid arthritis.

If the test was requested in the absence of a clear indication and the result is positive, it is important to bear in mind the potential pitfalls associated with that test and not attach a diagnostic label prematurely. None of the tests can confirm or exclude a condition, so the results should always be interpreted in the context of the whole clinical picture.   

Laboratory tests are often ordered inappropriately for patients in whom a rheumatologic illness is suspected; this occurs in both primary and secondary care.¹ Some tests are available both singly and as part of a battery of tests screening healthy people without symptoms.

The problem: negative test results are by no means always reassuring, and false-positive results raise the risks of unnecessary anxiety for patients and clinicians, needless referrals, and potential morbidity due to further unnecessary testing and exposure to wrong treatments.² Clinicians should be aware of the pitfalls of these tests in order to choose them wisely and interpret the results correctly.

This article provides practical guidance on requesting and interpreting some common tests in rheumatology, with the aid of case vignettes.

RHEUMATOID FACTOR AND ANTICITRULLINATED PEPTIDE ANTIBODY

A 41-year-old woman, previously in good health, presents to her primary care practitioner with a 6-week history of pain and swelling in her hands and early morning stiffness lasting about 2 hours. She denies having any extraarticular symptoms. Physical examination reveals synovitis across her right metacarpophalangeal joints, proximal interphalangeal joint of the left middle finger, and left wrist. The primary care physician is concerned that her symptoms might be due to rheumatoid arthritis.

Would testing for rheumatoid factor and anticitrullinated peptide antibody be useful in this patient?

Rheumatoid factor is an antibody (immunoglobulin M, IgG, or IgA) targeted against the Fc fragment of IgG.³ It was so named because it was originally detected in patients with rheumatoid arthritis, but it is neither sensitive nor specific for this condition. A meta-analysis of more than 5,000 patients with rheumatoid arthritis reported that rheumatoid factor testing had a sensitivity of 69% and specificity of 85%.⁴

Numerous other conditions can be associated with a positive test for rheumatoid factor (Table 1). Hence, a diagnosis of rheumatoid arthritis cannot be confirmed with a positive result alone, nor can it be excluded with a negative result.

Anticitrullinated peptide antibody, on the other hand, is much more specific for rheumatoid arthritis (95%), as it is seldom seen in other conditions, but its sensitivity is similar to that of rheumatoid factor (68%).^4–6 A positive result would thus lend strength to the diagnosis of rheumatoid arthritis, but a negative result would not exclude it.

Approach to early arthritis

When faced with a patient with early arthritis, some key questions to ask include^7,8:

Is this an inflammatory or a mechanical problem? Inflammatory arthritis is suggested by joint swelling that is not due to trauma or bony hypertrophy, early morning stiffness lasting longer than 30 minutes, and elevated inflammatory markers (erythrocyte sedimentation rate or C-reactive protein). Involvement of the small joints of the hands and feet may be suggested by pain on compression of the metacarpophalangeal and metatarsophalangeal joints, respectively.

Is there a definite identifiable underlying cause for the inflammatory arthritis? The pattern of development of joint symptoms or the presence of extraarticular symptoms may suggest an underlying problem such as gout, psoriatic arthritis, systemic lupus erythematosus, or sarcoidosis.

If the arthritis is undifferentiated (ie, there is no definite identifiable cause), is it likely to remit or persist? This is perhaps the most important question to ask in order to prognosticate. Patients with risk factors for persistent disease, ie, for development of rheumatoid arthritis, should be referred to a rheumatologist early for timely institution of disease-modifying antirheumatic drug therapy.⁹ Multiple studies have shown that patients in whom this therapy is started early have much better clinical, functional, and radiologic outcomes than those in whom it is delayed.^10–12

The revised American College of Rheumatology and European League Against Rheumatism criteria¹³ include the following factors as predictors of persistence:

• Number of involved joints (with greater weight given to involvement of small joints)
• Duration of symptoms 6 weeks or longer
• Elevated acute-phase response (erythrocyte sedimentation rate or C-reactive protein level)
• A positive serologic test (either rheumatoid factor or anticitrullinated peptide antibody).

If both rheumatoid factor and anticitrullinated peptide antibody are positive in a patient with early undifferentiated arthritis, the risk of progression to rheumatoid arthritis is almost 100%, thus underscoring the importance of testing for these antibodies.^5,6 Referral to a rheumatologist should, however, not be delayed in patients with negative test results (more than one-third of patients with rheumatoid arthritis may be negative for both), and should be considered in those with inflammatory joint symptoms persisting longer than 6 weeks, especially with involvement of the small joints (sparing the distal interphalangeals) and elevated acute-phase response.

Rheumatoid factor in healthy people without symptoms

In some countries, testing for rheumatoid factor is offered as part of a battery of screening tests in healthy people who have no symptoms, a practice that should be strongly discouraged.

Multiple studies, both prospective and retrospective, have demonstrated that both rheumatoid factor and anticitrullinated peptide antibody may be present several years before the clinical diagnosis of rheumatoid arthritis.^6,14–16 But the risk of developing rheumatoid arthritis for asymptomatic individuals who are rheumatoid factor-positive depends on the rheumatoid factor titer, positive family history of rheumatoid arthritis in first-degree relatives, and copresence of anticitrullinated peptide antibody. The absolute risk, nevertheless, is still very small. In some, there might be an alternative explanation such as undiagnosed Sjögren syndrome or hepatitis C.

In any event, no strategy is currently available that is proven to prevent the development of rheumatoid arthritis, and there is no role for disease-modifying therapy during the preclinical phase.¹⁶

Back to our patient

Blood testing in our patient reveals normal complete blood cell counts, aminotransferase levels, and serum creatinine concentration; findings on urinalysis are normal. Her erythrocyte sedimentation rate is 56 mm/hour (reference range 0–15), and her C-reactive protein level is 26 mg/dL (normal < 3). Testing is negative for rheumatoid factor and anticitrullinated peptide antibody.

Although her rheumatoid factor and anticitrullinated peptide antibody tests are negative, she is referred to a rheumatologist because she has predictors of persistent disease, ie, symptom duration of 6 weeks, involvement of the small joints of the hands, and elevated erythrocyte sedimentation rate and C-reactive protein. The rheumatologist checks her parvovirus serology, which is negative.

The patient is given parenteral depot corticosteroid therapy, to which she responds briefly. Because her symptoms persist and continue to worsen, methotrexate treatment is started after an additional 6 weeks.

 

 

ANTINUCLEAR ANTIBODY

A 37-year-old woman presents to her primary care physician with the complaint of tiredness. She has a family history of systemic lupus erythematosus in her sister and maternal aunt. She is understandably worried about lupus because of the family history and is asking to be tested for it.

Would testing for antinuclear antibody be reasonable?

Antinuclear antibody is not a single antibody but rather a family of autoantibodies that are directed against nuclear constituents such as single- or double-stranded deoxyribonucleic acid (dsDNA), histones, centromeres, proteins complexed with ribonucleic acid (RNA), and enzymes such as topoisomerase.^17,18

Protein antigens complexed with RNA and some enzymes in the nucleus are also known as extractable nuclear antigens (ENAs). They include Ro, La, Sm, Jo-1, RNP, and ScL-70 and are named after the patient in whom they were first discovered (Robert, Lavine, Smith, and John), the antigen that is targeted (ribonucleoprotein or RNP), and the disease with which they are associated (anti-ScL-70 or antitopoisomerase in diffuse cutaneous scleroderma).

Antinuclear antibody testing is commonly requested to exclude connective tissue diseases such as lupus, but the clinician needs to be aware of the following points:

Antinuclear antibody may be encountered in conditions other than lupus

These include¹⁹:

• Other autoimmune diseases such as rheumatoid arthritis, primary Sjögren syndrome, systemic sclerosis, autoimmune thyroid disease, and myasthenia gravis
• Infection with organisms that share the epitope with self-antigens (molecular mimicry)
• Cancers
• Drugs such as hydralazine, procainamide, and minocycline.

Antinuclear antibody might also be produced by the healthy immune system from time to time to clear the nuclear debris that is extruded from aging cells.

A study in healthy individuals²⁰ reported a prevalence of positive antinuclear antibody of 32% at a titer of 1/40, 15% at a titer of 1/80, 7% at a titer of 1/160, and 3% at a titer of 1/320. Importantly, a positive result was more common among family members of patients with autoimmune connective tissue diseases.²¹ Hence, a positive antinuclear antibody result does not always mean lupus.

Antinuclear antibody testing is highly sensitive for lupus

With current laboratory methods, antinuclear antibody testing has a sensitivity close to 100%. Hence, a negative result virtually rules out lupus.

Two methods are commonly used to test for antinuclear antibody: indirect immunofluorescence and enzyme-linked immunosorbent assay (ELISA).²² While human epithelial (Hep2) cells are used as the source of antigen in immunofluorescence, purified nuclear antigens coated on multiple-well plates are used in ELISA.

Although ELISA is simpler to perform, immunofluorescence has a slightly better sensitivity (because the Hep2 cells express a wide range of antigens) and is still considered the gold standard. As expected, the higher sensitivity occurs at the cost of reduced specificity (about 60%), so antinuclear antibody will also be detected in all the other conditions listed above.²³

To improve the specificity of antinuclear antibody testing, laboratories report titers (the highest dilution of the test serum that tested positive); a cutoff of greater than 1/80 is generally considered significant.

Do not order antinuclear antibody testing indiscriminately

If the antinuclear antibody test is requested indiscriminately, the positive predictive value for the diagnosis of lupus is only 11%.²⁴ The test should be requested only when the pretest probability of lupus or other connective tissue disease is high. The positive predictive value is much higher in patients presenting with clinical or laboratory manifestations involving 2 or more organ systems (Table 2).^18,25

Categorization of the specific antigen target improves disease specificity. The antinuclear antibody in patients with lupus may be targeted against single- or double-stranded DNA, histones, or 1 or more of the ENAs. Among these, the presence of anti-dsDNA or anti-Sm is highly specific for a diagnosis of lupus (close to 100%). Neither is sensitive for lupus, however, with anti-dsDNA present in only 60% of patients with lupus and anti-Sm in about 30%.¹⁷ Hence, patients with a positive antinuclear antibody and negative anti-dsDNA and anti-Sm may continue to pose a diagnostic challenge. Other examples of specific disease associations are listed in Table 3.

To sum up, the antinuclear antibody test should be requested only in patients with involvement of multiple organ systems. Although a negative result would make it extremely unlikely that the clinical presentation is due to lupus, a positive result is insufficient on its own to make a diagnosis of lupus.

Diagnosing lupus is straightforward when patients present with a specific manifestation such as inflammatory arthritis, photosensitive skin rash, hemolytic anemia, thrombocytopenia, or nephritis, or with specific antibodies such as those against dsDNA or Sm. Patients who present with nonspecific symptoms such as arthralgia or tiredness with a positive antinuclear antibody and negative anti-dsDNA and anti-Sm may present difficulties even for the specialist.^25–27

Back to our patient

Our patient denies arthralgia. She has no extraarticular symptoms such as skin rashes, oral ulcers, sicca symptoms, muscle weakness, Raynaud phenomenon, pleuritic chest pain, or breathlessness. Findings on physical examination and urinalysis are unremarkable.

Her primary care physician decides to check her complete blood cell count, erythrocyte sedimentation rate, and thyroid-stimulating hormone level. Although she is reassured that her tiredness is not due to lupus, she insists on getting an antinuclear antibody test.

Her complete blood cell counts are normal. Her erythrocyte sedimentation rate is 6 mm/hour. However, her thyroid-stimulating hormone level is elevated, and subsequent testing shows low free thyroxine and positive thyroid peroxidase antibodies. The antinuclear antibody is positive in a titer of 1/80 and negative for anti-dsDNA and anti-ENA.

We explain to her that the positive antinuclear antibody is most likely related to her autoimmune thyroid disease. She is referred to an endocrinologist.

 

 

ANTIPHOSPHOLIPID ANTIBODIES

A 24-year-old woman presents to the emergency department with acute unprovoked deep vein thrombosis in her right leg, confirmed by ultrasonography. She has no history of previous thrombosis, and the relevant family history is unremarkable. She has never been pregnant. Her platelet count is 84 × 10⁹/L (reference range 150–400), and her baseline activated partial thromboplastin time is prolonged at 62 seconds (reference range 23.0–32.4). The rest of her blood counts and her prothrombin time, liver enzyme levels, and serum creatinine level are normal.

Should this patient be tested for antiphospholipid antibodies?

Antiphospholipid antibodies are important because of their association with thrombotic risk (both venous and arterial) and pregnancy morbidity. The name is a misnomer, as these antibodies are targeted against some proteins that are bound to phospholipids and not only to the phospholipids themselves.

According to the modified Sapporo criteria for the classification of antiphospholipid syndrome,²⁸ antiphospholipid antibodies should remain persistently positive on at least 2 separate occasions at least 12 weeks apart for the result to be considered significant because some infections and drugs may be associated with the transient presence of antiphospholipid antibodies.

Screening for antiphospholipid antibodies should include testing for IgM and IgG anticardiolipin antibodies, lupus anticoagulant, and IgM and IgG beta-2 glycoprotein I antibodies.^29,30

Anticardiolipin antibodies

Anticardiolipin (aCL) antibodies may be targeted either against beta-2 glycoprotein I (beta-2GPI) that is bound to cardiolipin (a phospholipid) or against cardiolipin alone; the former is more specific. Antibodies directed against cardiolipin alone are usually transient and are associated with infections and drugs. The result is considered significant only when anticardiolipin antibodies are present in a medium to high titer (> 40 IgG phospholipid units or IgM phospholipid units, or > 99th percentile).

Lupus anticoagulant

The antibody with “lupus anticoagulant activity” is targeted against prothrombin plus phospholipid or beta-2GPI plus phospholipid. The test for it is a functional assay involving 3 steps:

Demonstrating the prolongation of a phospholipid-dependent coagulation assay like the activated partial thromboplastin time (aPTT). (This may explain the prolongation of aPTT in the patient described in the vignette.) Although the presence of lupus anticoagulant is associated with thrombosis, it is called an “anticoagulant” because of this in vitro prolongation of phospholipid-dependent coagulation assays.

Mixing study. The phospholipid-dependent coagulation assay could be prolonged because of either the deficiency of a coagulation factor or the presence of the antiphospholipid antibodies. This can be differentiated by mixing the patient’s plasma with normal plasma (which will have all the clotting factors) in a 1:1 ratio. If the coagulation assay remains prolonged after the addition of normal plasma, clotting factor deficiency can be excluded.

Addition of a phospholipid. If the prolongation of the coagulation assay is due to the presence of an antiphospholipid antibody, addition of extra phospholipid will correct this.

Beta-2 glycoprotein I antibody (anti-beta-2GPI)

The beta-2GPI that is not bound to the cardiolipin can be detected by separately testing for beta-2GPI (the anticardiolipin test only detects the beta-2GPI that is bound to the cardiolipin). The result is considered significant if beta-2GPI is present in a medium to high titer (> 99th percentile).

Studies have shown that antiphospholipid antibodies may be present in 1% to 5% of apparently healthy people in the general population.³¹ These are usually low-titer anticardiolipin or anti-beta-GPI IgM antibodies that are not associated with thrombosis or adverse pregnancy outcomes. Hence, the term antiphospholipid syndrome should be reserved for those who have had at least 1 episode of thrombosis or pregnancy morbidity and persistent antiphospholipid antibodies, and not those who have asymptomatic or transient antiphospholipid antibodies.

Triple positivity (positive anticardiolipin, lupus anticoagulant, and anti-beta-2GPI) seems to be associated with the highest risk of thrombosis, with a 10-year cumulative incidence of 37.1% (95% confidence interval [CI] 19.9–54.3) for a first thrombotic event,³² and 44.2% (95% CI 38.6–49.8) for recurrent thrombosis.³³

The association with thrombosis is stronger for lupus anticoagulant than with the other 2 antibodies, with different studies³⁴ finding an odds ratio ranging from 5 to 16. A positive lupus anticoagulant test with or without a moderate to high titer of anticardiolipin or anti-beta-2GPI IgM or IgG constitutes a high-risk profile, while a moderate to high titer of anticardiolipin or anti-beta-2GPI IgM or IgG constitutes a moderate-risk profile. A low titer of anticardiolipin or anti-beta-2GPI IgM or IgG constitutes a low-risk profile that may not be associated with thrombosis.³⁵

Antiphospholipid syndrome is important to recognize because of the need for long-term anticoagulation to prevent recurrence.³⁶ It may be primary, when it occurs on its own, or secondary, when it occurs in association with another autoimmune disease such as lupus.

Venous events in antiphospholipid syndrome most commonly manifest as lower-limb deep vein thrombosis or pulmonary embolism, while arterial events most commonly manifest as stroke or transient ischemic attack.³⁷ Obstetric manifestations may include not only miscarriage and stillbirth, but also preterm delivery, intrauterine growth retardation, and preeclampsia, all occurring due to placental insufficiency.

The frequency of antiphospholipid antibodies has been estimated as 13.5% in patients with stroke, 11% with myocardial infarction, 9.5% with deep vein thrombosis, and 6% for those with pregnancy morbidity.³⁸

Some noncriteria manifestations have also been recognized in antiphospholipid syndrome, such as thrombocytopenia, cardiac vegetations (Libman-Sachs endocarditis), livedo reticularis, and nephropathy.

The indications for antiphospholipid antibody testing are listed in Table 4.²⁹ For the patient described in the vignette, it would be appropriate to test for antiphospholipid antibodies because of her unprovoked thrombosis, thrombocytopenia, and prolonged aPTT. Anticoagulant treatment is known to be associated with false-positive lupus anticoagulant, so any blood samples should be drawn before such treatment is commenced.

Back to our patient

Our patient’s anticardiolipin IgG test is negative, while her lupus anticoagulant and beta-2GPI IgG are positive. She has no clinical or laboratory features suggesting lupus.

She is started on warfarin. After 3 months, the warfarin is interrupted for several days, and she is retested for all 3 antiphospholipid antibodies. Her beta-2GPI I IgG and lupus anticoagulant tests are again positive. Because of the persistent antiphospholipid antibody positivity and clinical history of deep vein thrombosis, her condition is diagnosed as primary antiphospholipid syndrome. She is advised to continue anticoagulant therapy indefinitely.

 

 

ANTINEUTROPHIL CYTOPLASMIC ANTIBODY

A 34-year-old man who is an injecting drug user presents with a 2-week history of fever, malaise, and generalized arthralgia. There are no localizing symptoms of infection. Notable findings on examination include a temperature of 38.0°C (100.4°F), needle track marks in his arms, nonblanching vasculitic rash in his legs, and a systolic murmur over the precordium.

His white blood cell count is 15.3 × 10⁹/L (reference range 3.7–11.0), and his C-reactive protein level is 234 mg/dL (normal < 3). Otherwise, results of blood cell counts, liver enzyme tests, renal function tests, urinalysis, and chest radiography are normal.

Two sets of blood cultures are drawn. Transthoracic echocardiography and the antineutrophil cytoplasmic antibody (ANCA) test are requested, as are screening tests for human immunodeficiency virus, hepatitis B, and hepatitis C.

Was the ANCA test indicated in this patient?

ANCAs are autoantibodies against antigens located in the cytoplasmic granules of neutrophils and monocytes. They are associated with small-vessel vasculitides such as granulomatosis with polyangiitis (GPA), microscopic polyangiitis (MPA), eosinophilic granulomatosis with polyangiitis (EGPA), and isolated pauciimmune crescentic glomerulonephritis, all collectively known as ANCA-associated vasculitis (AAV).³⁹

Laboratory methods to detect ANCA include indirect immunofluorescence and antigen-specific enzyme immunoassays. Indirect immunofluorescence only tells us whether or not an antibody that is targeting a cytoplasmic antigen is present. Based on the indirect immunofluorescent pattern, ANCA can be classified as follows:

• Perinuclear or p-ANCA (if the targeted antigen is located just around the nucleus and extends into it)
• Cytoplasmic or c-ANCA (if the targeted antigen is located farther away from the nucleus)
• Atypical ANCA (if the indirect immunofluorescent pattern does not fit with either p-ANCA or c-ANCA).

Indirect immunofluorescence does not give information about the exact antigen that is targeted; this can only be obtained by performing 1 of the antigen-specific immunoassays. The target antigen for c-ANCA is usually proteinase-3 (PR3), while that for p-ANCA could be myeloperoxidase (MPO), cathepsin, lysozyme, lactoferrin, or bactericidal permeability inhibitor. Anti-PR3 is highly specific for GPA, while anti-MPO is usually associated with MPA and EGPA. Less commonly, anti-PR3 may be seen in patients with MPA and anti-MPO in those with GPA. Hence, there is an increasing trend toward classifying ANCA-associated vasculitis into PR3-associated or MPO-associated vasculitis rather than as GPA, MPA, EGPA, or renal-limited vasculitis.⁴⁰

Several audits have shown that the ANCA test is widely misused and requested indiscriminately to rule out vasculitis. This results in a lower positive predictive value, possible harm to patients due to increased false-positive rates, and increased burden on the laboratory.^41–43 At least 2 separate groups have demonstrated that a gating policy that refuses ANCA testing in patients without clinical evidence of systemic vasculitis can reduce the number of inappropriate requests, improve the diagnostic yield, and make it more clinically relevant and cost-effective.^44,45

The clinician should bear in mind that:

ANCA testing should be requested only if the pretest probability of ANCA-associated vasculitis is high. The indications proposed by the International Consensus Statement on ANCA testing⁴⁶ are listed in Table 5. These criteria have been clinically validated, with 1 study even demonstrating that no cases of ANCA-associated vasculitis would be missed if these guidelines are followed.⁴⁷

Current guidelines recommend using one of the antigen-specific assays for PR3 and MPO as the primary screening method.⁴⁸ Until recently, indirect immunofluorescence was used to screen for ANCA-associated vasculitis, and positive results were confirmed by ELISA to detect ANCAs specific for PR3 and MPO,⁴⁹ but this is no longer recommended because of recent evidence suggesting a large variability between the different indirect immunofluorescent methods and improved diagnostic performance of the antigen-specific assays.

In a large multicenter study by Damoiseaux et al, the specificity with the different antigen-specific immunoassays was 98% to 99% for PR3-ANCA and 96% to 99% for MPO-ANCA.⁵⁰

ANCA-associated vasculitis should not be considered excluded if the PR3 and MPO-ANCA are negative. In the Damoiseaux study, about 11% to 15% of patients with GPA and 8% to 24% of patients with MPA tested negative for both PR3 and MPO-ANCA.⁵⁰

If the ANCA result is negative and clinical suspicion for ANCA-associated vasculitis is high, the clinician may wish to consider requesting another immunoassay method or indirect immunofluorescence. Results of indirect immunofluorescent testing results may be positive in those with a negative immunoassay, and vice versa.

A positive ANCA result is not diagnostic of ANCA-associated vasculitis. Numerous other conditions are associated with ANCA, usually p-ANCA or atypical ANCA (Table 6). The antigens targeted by these ANCAs are usually cathepsin, lysozyme, lactoferrin, and bactericidal permeability inhibitor.

Thus, the ANCA result should always be interpreted in the context of the whole clinical picture.⁵¹ Biopsy should still be considered the gold standard for the diagnosis of ANCA-associated vasculitis. The ANCA titer can help to improve clinical interpretation, because the likelihood of ANCA-associated vasculitis increases with higher levels of PR3 and MPO-ANCA.⁵²

Back to our patient

Our patient’s blood cultures grow methicillin-sensitive Staphylococcus aureus in both sets after 48 hours. Transthoracic echocardiography reveals vegetations around the tricuspid valve, with no evidence of valvular regurgitation. The diagnosis is right-sided infective endocarditis. He is started on appropriate antibiotics.

Tests for human immunodeficiency virus, hepatitis B, and hepatitis C are negative. The ANCA test is positive for MPO-ANCA at 28 IU/mL (normal < 10).

The positive ANCA is thought to be related to the infective endocarditis. His vasculitis is most likely secondary to infective endocarditis and not ANCA-associated vasculitis. The ANCA test need not have been requested in the first place.

 

 

HUMAN LEUKOCYTE ANTIGEN-B27

A 22-year-old man presents to his primary care physician with a 4-month history of gradually worsening low back pain associated with early morning stiffness lasting more than 2 hours. He has no peripheral joint symptoms.

In the last 2 years, he has had 2 separate episodes of uveitis. There is a family history of ankylosing spondylitis in his father. Examination reveals global restriction of lumbar movements but is otherwise unremarkable. Magnetic resonance imaging (MRI) of the lumbar spine and sacroiliac joints is normal.

Should this patient be tested for human leukocyte antigen-B27 (HLA-B27)?

The major histocompatibility complex (MHC) is a gene complex that is present in all animals. It encodes proteins that help with immunologic tolerance. HLA simply refers to the human version of the MHC.⁵³ The HLA gene complex, located on chromosome 6, is categorized into class I, class II, and class III. HLA-B is one of the 3 class I genes. Thus, a positive HLA-B27 result simply means that the particular gene is present in that person.

HLA-B27 is strongly associated with ankylosing spondylitis, also known as axial spondyloarthropathy.⁵⁴ Other genes also contribute to the pathogenesis of ankylosing spondylitis, but HLA-B27 is present in more than 90% of patients with this disease and is by far considered the most important. The association is not as strong for peripheral spondyloarthropathy, with studies reporting a frequency of up to 75% for reactive arthritis and inflammatory bowel disease-associated arthritis, and up to 50% for psoriatic arthritis and uveitis.⁵⁵

About 9% of healthy, asymptomatic individuals may have HLA-B27, so the mere presence of this gene is not evidence of disease.⁵⁶ There may be up to a 20-fold increased risk of ankylosing spondylitis among those who are HLA-B27-positive.⁵⁷

Some HLA genes have many different alleles, each of which is given a number (explaining the number 27 that follows the B). Closely related alleles that differ from one another by only a few amino-acid substitutions are then categorized together, thus accounting for more than 100 subtypes of HLA-B27 (designated from HLA-B*2701 to HLA-B*27106). These subtypes vary in frequency among different racial groups, and the population prevalence of ankylosing spondylitis parallels the frequency of HLA-B27.⁵⁸ The most common subtype seen in white people and American Indians is B*2705. HLA-B27 is rare in blacks, explaining the rarity of ankylosing spondylitis in this population. Further examples include HLA-B*2704, which is seen in Asians, and HLA-B*2702, seen in Mediterranean populations. Not all subtypes of HLA-B27 are associated with disease, and some, like HLA-B*2706, may also be protective.

When should the clinician consider testing for HLA-B27?

Not all patients with low back pain need an HLA-B27 test. First, it is important to look for clinical features of axial spondyloarthropathy (Table 7). The unifying feature of spondyloarthropathy is enthesitis (inflammation at the sites of insertion of tendons or ligaments on the skeleton). Inflammation of axial entheses causes spondylitis and sacroiliitis, manifesting as inflammatory back pain. Clinical clues to inflammatory back pain include insidious onset, aggravation with rest or inactivity, prolonged early morning stiffness, disturbed sleep during the second half of the night, relief with movement or activity, alternating gluteal pain (due to sacroiliitis), and good response to anti-inflammatory medication (although nonspecific).

Peripheral spondyloarthropathy may present with arthritis, enthesitis (eg, heel pain due to inflammation at the site of insertion of the Achilles tendon or plantar fascia), or dactylitis (“sausage” swelling of the whole finger or toe due to extension of inflammation beyond the margins of the joint). Other clues may include psoriasis, inflammatory bowel disease, history of preceding gastrointestinal or genitourinary infection, family history of similar conditions, and history of recurrent uveitis.

For the initial assessment of patients who have inflammatory back pain, plain radiography of the sacroiliac joints is considered the gold standard.⁵⁹ If plain radiography does not show evidence of sacroiliitis, MRI of the sacroiliac joints should be considered. While plain radiography can reveal only structural changes such as sclerosis, erosions, and ankylosis, MRI is useful to evaluate for early inflammatory changes such as bone marrow edema. Imaging the lumbar spine is not necessary, as the sacroiliac joints are almost invariably involved in axial spondyloarthropathy, and lesions seldom occur in the lumbar spine in isolation.⁶⁰

The diagnosis of ankylosing spondylitis previously relied on confirmatory imaging features, but based on the new International Society classification criteria,^61–63 which can be applied to patients with more than 3 months of back pain and age of onset of symptoms before age 45, patients can be classified as having 1 of the following:

• Radiographic axial spondyloarthropathy, if they have evidence of sacroiliitis on imaging plus 1 other feature of spondyloarthropathy
• Nonradiographic axial spondyloarthropathy, if they have a positive HLA-B27 plus 2 other features of spondyloarthropathy (Table 7).

These new criteria have a sensitivity of 82.9% and specificity of 84.4%.^62,63 The disease burden of radiographic and nonradiographic axial spondyloarthropathy has been shown to be similar, suggesting that they are part of the same disease spectrum. Thus, the HLA-B27 test is useful to make a diagnosis of axial spondyloarthropathy even in the absence of imaging features and could be requested in patients with 2 or more features of spondyloarthropathy. In the absence of imaging features and a negative HLA-B27 result, however, the patient cannot be classified as having axial spondyloarthropathy.

Back to our patient

The absence of radiographic evidence would not exclude axial spondyloarthropathy in our patient. The HLA-B27 test is requested because of the inflammatory back pain and the presence of 2 spondyloarthropathy features (uveitis and the family history) and is reported to be positive. His disease is classified as nonradiographic axial spondyloarthropathy.

He is started on regular naproxen and is referred to a physiotherapist. After 1 month, he reports significant symptomatic improvement. He asks if he can be retested for HLA-B27 to see if it has become negative. We tell him that there is no point in repeating it, as it is a gene and will not disappear.

SUMMARY: CONSIDER THE CLINICAL PICTURE

When approaching a patient suspected of having a rheumatologic disease, a clinician should first consider the clinical presentation and the intended purpose of each test. The tests, in general, might serve several purposes. They might help to:

Increase the likelihood of the diagnosis in question. For example, a positive rheumatoid factor or anticitrullinated peptide antibody can help diagnose rheumatoid arthritis in a patient with early polyarthritis, a positive HLA-B27 can help diagnose ankylosing spondylitis in patients with inflammatory back pain and normal imaging, and a positive ANCA can help diagnose ANCA-associated vasculitis in a patient with glomerulonephritis.

Reduce the likelihood of the diagnosis in question. For example, a negative antinuclear antibody test reduces the likelihood of lupus in a patient with joint pains.

Monitor the condition. For example DNA antibodies can be used to monitor the activity of lupus.

Plan the treatment strategy. For example, one might consider lifelong anticoagulation if antiphospholipid antibodies are persistently positive in a patient with thrombosis.

Prognosticate. For example, positive rheumatoid factor and anticitrullinated peptide antibody increase the risk of erosive rheumatoid arthritis.

If the test was requested in the absence of a clear indication and the result is positive, it is important to bear in mind the potential pitfalls associated with that test and not attach a diagnostic label prematurely. None of the tests can confirm or exclude a condition, so the results should always be interpreted in the context of the whole clinical picture.   

Laboratory tests are often ordered inappropriately for patients in whom a rheumatologic illness is suspected; this occurs in both primary and secondary care.¹ Some tests are available both singly and as part of a battery of tests screening healthy people without symptoms.

The problem: negative test results are by no means always reassuring, and false-positive results raise the risks of unnecessary anxiety for patients and clinicians, needless referrals, and potential morbidity due to further unnecessary testing and exposure to wrong treatments.² Clinicians should be aware of the pitfalls of these tests in order to choose them wisely and interpret the results correctly.

This article provides practical guidance on requesting and interpreting some common tests in rheumatology, with the aid of case vignettes.

RHEUMATOID FACTOR AND ANTICITRULLINATED PEPTIDE ANTIBODY

A 41-year-old woman, previously in good health, presents to her primary care practitioner with a 6-week history of pain and swelling in her hands and early morning stiffness lasting about 2 hours. She denies having any extraarticular symptoms. Physical examination reveals synovitis across her right metacarpophalangeal joints, proximal interphalangeal joint of the left middle finger, and left wrist. The primary care physician is concerned that her symptoms might be due to rheumatoid arthritis.

Would testing for rheumatoid factor and anticitrullinated peptide antibody be useful in this patient?

Rheumatoid factor is an antibody (immunoglobulin M, IgG, or IgA) targeted against the Fc fragment of IgG.³ It was so named because it was originally detected in patients with rheumatoid arthritis, but it is neither sensitive nor specific for this condition. A meta-analysis of more than 5,000 patients with rheumatoid arthritis reported that rheumatoid factor testing had a sensitivity of 69% and specificity of 85%.⁴

Numerous other conditions can be associated with a positive test for rheumatoid factor (Table 1). Hence, a diagnosis of rheumatoid arthritis cannot be confirmed with a positive result alone, nor can it be excluded with a negative result.

Anticitrullinated peptide antibody, on the other hand, is much more specific for rheumatoid arthritis (95%), as it is seldom seen in other conditions, but its sensitivity is similar to that of rheumatoid factor (68%).^4–6 A positive result would thus lend strength to the diagnosis of rheumatoid arthritis, but a negative result would not exclude it.

Approach to early arthritis

When faced with a patient with early arthritis, some key questions to ask include^7,8:

Is this an inflammatory or a mechanical problem? Inflammatory arthritis is suggested by joint swelling that is not due to trauma or bony hypertrophy, early morning stiffness lasting longer than 30 minutes, and elevated inflammatory markers (erythrocyte sedimentation rate or C-reactive protein). Involvement of the small joints of the hands and feet may be suggested by pain on compression of the metacarpophalangeal and metatarsophalangeal joints, respectively.

Is there a definite identifiable underlying cause for the inflammatory arthritis? The pattern of development of joint symptoms or the presence of extraarticular symptoms may suggest an underlying problem such as gout, psoriatic arthritis, systemic lupus erythematosus, or sarcoidosis.

If the arthritis is undifferentiated (ie, there is no definite identifiable cause), is it likely to remit or persist? This is perhaps the most important question to ask in order to prognosticate. Patients with risk factors for persistent disease, ie, for development of rheumatoid arthritis, should be referred to a rheumatologist early for timely institution of disease-modifying antirheumatic drug therapy.⁹ Multiple studies have shown that patients in whom this therapy is started early have much better clinical, functional, and radiologic outcomes than those in whom it is delayed.^10–12

The revised American College of Rheumatology and European League Against Rheumatism criteria¹³ include the following factors as predictors of persistence:

• Number of involved joints (with greater weight given to involvement of small joints)
• Duration of symptoms 6 weeks or longer
• Elevated acute-phase response (erythrocyte sedimentation rate or C-reactive protein level)
• A positive serologic test (either rheumatoid factor or anticitrullinated peptide antibody).

If both rheumatoid factor and anticitrullinated peptide antibody are positive in a patient with early undifferentiated arthritis, the risk of progression to rheumatoid arthritis is almost 100%, thus underscoring the importance of testing for these antibodies.^5,6 Referral to a rheumatologist should, however, not be delayed in patients with negative test results (more than one-third of patients with rheumatoid arthritis may be negative for both), and should be considered in those with inflammatory joint symptoms persisting longer than 6 weeks, especially with involvement of the small joints (sparing the distal interphalangeals) and elevated acute-phase response.

Rheumatoid factor in healthy people without symptoms

In some countries, testing for rheumatoid factor is offered as part of a battery of screening tests in healthy people who have no symptoms, a practice that should be strongly discouraged.

Multiple studies, both prospective and retrospective, have demonstrated that both rheumatoid factor and anticitrullinated peptide antibody may be present several years before the clinical diagnosis of rheumatoid arthritis.^6,14–16 But the risk of developing rheumatoid arthritis for asymptomatic individuals who are rheumatoid factor-positive depends on the rheumatoid factor titer, positive family history of rheumatoid arthritis in first-degree relatives, and copresence of anticitrullinated peptide antibody. The absolute risk, nevertheless, is still very small. In some, there might be an alternative explanation such as undiagnosed Sjögren syndrome or hepatitis C.

In any event, no strategy is currently available that is proven to prevent the development of rheumatoid arthritis, and there is no role for disease-modifying therapy during the preclinical phase.¹⁶

Back to our patient

Blood testing in our patient reveals normal complete blood cell counts, aminotransferase levels, and serum creatinine concentration; findings on urinalysis are normal. Her erythrocyte sedimentation rate is 56 mm/hour (reference range 0–15), and her C-reactive protein level is 26 mg/dL (normal < 3). Testing is negative for rheumatoid factor and anticitrullinated peptide antibody.

Although her rheumatoid factor and anticitrullinated peptide antibody tests are negative, she is referred to a rheumatologist because she has predictors of persistent disease, ie, symptom duration of 6 weeks, involvement of the small joints of the hands, and elevated erythrocyte sedimentation rate and C-reactive protein. The rheumatologist checks her parvovirus serology, which is negative.

The patient is given parenteral depot corticosteroid therapy, to which she responds briefly. Because her symptoms persist and continue to worsen, methotrexate treatment is started after an additional 6 weeks.

 

 

ANTINUCLEAR ANTIBODY

A 37-year-old woman presents to her primary care physician with the complaint of tiredness. She has a family history of systemic lupus erythematosus in her sister and maternal aunt. She is understandably worried about lupus because of the family history and is asking to be tested for it.

Would testing for antinuclear antibody be reasonable?

Antinuclear antibody is not a single antibody but rather a family of autoantibodies that are directed against nuclear constituents such as single- or double-stranded deoxyribonucleic acid (dsDNA), histones, centromeres, proteins complexed with ribonucleic acid (RNA), and enzymes such as topoisomerase.^17,18

Protein antigens complexed with RNA and some enzymes in the nucleus are also known as extractable nuclear antigens (ENAs). They include Ro, La, Sm, Jo-1, RNP, and ScL-70 and are named after the patient in whom they were first discovered (Robert, Lavine, Smith, and John), the antigen that is targeted (ribonucleoprotein or RNP), and the disease with which they are associated (anti-ScL-70 or antitopoisomerase in diffuse cutaneous scleroderma).

Antinuclear antibody testing is commonly requested to exclude connective tissue diseases such as lupus, but the clinician needs to be aware of the following points:

Antinuclear antibody may be encountered in conditions other than lupus

These include¹⁹:

• Other autoimmune diseases such as rheumatoid arthritis, primary Sjögren syndrome, systemic sclerosis, autoimmune thyroid disease, and myasthenia gravis
• Infection with organisms that share the epitope with self-antigens (molecular mimicry)
• Cancers
• Drugs such as hydralazine, procainamide, and minocycline.

Antinuclear antibody might also be produced by the healthy immune system from time to time to clear the nuclear debris that is extruded from aging cells.

A study in healthy individuals²⁰ reported a prevalence of positive antinuclear antibody of 32% at a titer of 1/40, 15% at a titer of 1/80, 7% at a titer of 1/160, and 3% at a titer of 1/320. Importantly, a positive result was more common among family members of patients with autoimmune connective tissue diseases.²¹ Hence, a positive antinuclear antibody result does not always mean lupus.

Antinuclear antibody testing is highly sensitive for lupus

With current laboratory methods, antinuclear antibody testing has a sensitivity close to 100%. Hence, a negative result virtually rules out lupus.

Two methods are commonly used to test for antinuclear antibody: indirect immunofluorescence and enzyme-linked immunosorbent assay (ELISA).²² While human epithelial (Hep2) cells are used as the source of antigen in immunofluorescence, purified nuclear antigens coated on multiple-well plates are used in ELISA.

Although ELISA is simpler to perform, immunofluorescence has a slightly better sensitivity (because the Hep2 cells express a wide range of antigens) and is still considered the gold standard. As expected, the higher sensitivity occurs at the cost of reduced specificity (about 60%), so antinuclear antibody will also be detected in all the other conditions listed above.²³

To improve the specificity of antinuclear antibody testing, laboratories report titers (the highest dilution of the test serum that tested positive); a cutoff of greater than 1/80 is generally considered significant.

Do not order antinuclear antibody testing indiscriminately

If the antinuclear antibody test is requested indiscriminately, the positive predictive value for the diagnosis of lupus is only 11%.²⁴ The test should be requested only when the pretest probability of lupus or other connective tissue disease is high. The positive predictive value is much higher in patients presenting with clinical or laboratory manifestations involving 2 or more organ systems (Table 2).^18,25

Categorization of the specific antigen target improves disease specificity. The antinuclear antibody in patients with lupus may be targeted against single- or double-stranded DNA, histones, or 1 or more of the ENAs. Among these, the presence of anti-dsDNA or anti-Sm is highly specific for a diagnosis of lupus (close to 100%). Neither is sensitive for lupus, however, with anti-dsDNA present in only 60% of patients with lupus and anti-Sm in about 30%.¹⁷ Hence, patients with a positive antinuclear antibody and negative anti-dsDNA and anti-Sm may continue to pose a diagnostic challenge. Other examples of specific disease associations are listed in Table 3.

To sum up, the antinuclear antibody test should be requested only in patients with involvement of multiple organ systems. Although a negative result would make it extremely unlikely that the clinical presentation is due to lupus, a positive result is insufficient on its own to make a diagnosis of lupus.

Diagnosing lupus is straightforward when patients present with a specific manifestation such as inflammatory arthritis, photosensitive skin rash, hemolytic anemia, thrombocytopenia, or nephritis, or with specific antibodies such as those against dsDNA or Sm. Patients who present with nonspecific symptoms such as arthralgia or tiredness with a positive antinuclear antibody and negative anti-dsDNA and anti-Sm may present difficulties even for the specialist.^25–27

Back to our patient

Our patient denies arthralgia. She has no extraarticular symptoms such as skin rashes, oral ulcers, sicca symptoms, muscle weakness, Raynaud phenomenon, pleuritic chest pain, or breathlessness. Findings on physical examination and urinalysis are unremarkable.

Her primary care physician decides to check her complete blood cell count, erythrocyte sedimentation rate, and thyroid-stimulating hormone level. Although she is reassured that her tiredness is not due to lupus, she insists on getting an antinuclear antibody test.

Her complete blood cell counts are normal. Her erythrocyte sedimentation rate is 6 mm/hour. However, her thyroid-stimulating hormone level is elevated, and subsequent testing shows low free thyroxine and positive thyroid peroxidase antibodies. The antinuclear antibody is positive in a titer of 1/80 and negative for anti-dsDNA and anti-ENA.

We explain to her that the positive antinuclear antibody is most likely related to her autoimmune thyroid disease. She is referred to an endocrinologist.

 

 

ANTIPHOSPHOLIPID ANTIBODIES

A 24-year-old woman presents to the emergency department with acute unprovoked deep vein thrombosis in her right leg, confirmed by ultrasonography. She has no history of previous thrombosis, and the relevant family history is unremarkable. She has never been pregnant. Her platelet count is 84 × 10⁹/L (reference range 150–400), and her baseline activated partial thromboplastin time is prolonged at 62 seconds (reference range 23.0–32.4). The rest of her blood counts and her prothrombin time, liver enzyme levels, and serum creatinine level are normal.

Should this patient be tested for antiphospholipid antibodies?

Antiphospholipid antibodies are important because of their association with thrombotic risk (both venous and arterial) and pregnancy morbidity. The name is a misnomer, as these antibodies are targeted against some proteins that are bound to phospholipids and not only to the phospholipids themselves.

According to the modified Sapporo criteria for the classification of antiphospholipid syndrome,²⁸ antiphospholipid antibodies should remain persistently positive on at least 2 separate occasions at least 12 weeks apart for the result to be considered significant because some infections and drugs may be associated with the transient presence of antiphospholipid antibodies.

Screening for antiphospholipid antibodies should include testing for IgM and IgG anticardiolipin antibodies, lupus anticoagulant, and IgM and IgG beta-2 glycoprotein I antibodies.^29,30

Anticardiolipin antibodies

Anticardiolipin (aCL) antibodies may be targeted either against beta-2 glycoprotein I (beta-2GPI) that is bound to cardiolipin (a phospholipid) or against cardiolipin alone; the former is more specific. Antibodies directed against cardiolipin alone are usually transient and are associated with infections and drugs. The result is considered significant only when anticardiolipin antibodies are present in a medium to high titer (> 40 IgG phospholipid units or IgM phospholipid units, or > 99th percentile).

Lupus anticoagulant

The antibody with “lupus anticoagulant activity” is targeted against prothrombin plus phospholipid or beta-2GPI plus phospholipid. The test for it is a functional assay involving 3 steps:

Demonstrating the prolongation of a phospholipid-dependent coagulation assay like the activated partial thromboplastin time (aPTT). (This may explain the prolongation of aPTT in the patient described in the vignette.) Although the presence of lupus anticoagulant is associated with thrombosis, it is called an “anticoagulant” because of this in vitro prolongation of phospholipid-dependent coagulation assays.

Mixing study. The phospholipid-dependent coagulation assay could be prolonged because of either the deficiency of a coagulation factor or the presence of the antiphospholipid antibodies. This can be differentiated by mixing the patient’s plasma with normal plasma (which will have all the clotting factors) in a 1:1 ratio. If the coagulation assay remains prolonged after the addition of normal plasma, clotting factor deficiency can be excluded.

Addition of a phospholipid. If the prolongation of the coagulation assay is due to the presence of an antiphospholipid antibody, addition of extra phospholipid will correct this.

Beta-2 glycoprotein I antibody (anti-beta-2GPI)

The beta-2GPI that is not bound to the cardiolipin can be detected by separately testing for beta-2GPI (the anticardiolipin test only detects the beta-2GPI that is bound to the cardiolipin). The result is considered significant if beta-2GPI is present in a medium to high titer (> 99th percentile).

Studies have shown that antiphospholipid antibodies may be present in 1% to 5% of apparently healthy people in the general population.³¹ These are usually low-titer anticardiolipin or anti-beta-GPI IgM antibodies that are not associated with thrombosis or adverse pregnancy outcomes. Hence, the term antiphospholipid syndrome should be reserved for those who have had at least 1 episode of thrombosis or pregnancy morbidity and persistent antiphospholipid antibodies, and not those who have asymptomatic or transient antiphospholipid antibodies.

Triple positivity (positive anticardiolipin, lupus anticoagulant, and anti-beta-2GPI) seems to be associated with the highest risk of thrombosis, with a 10-year cumulative incidence of 37.1% (95% confidence interval [CI] 19.9–54.3) for a first thrombotic event,³² and 44.2% (95% CI 38.6–49.8) for recurrent thrombosis.³³

The association with thrombosis is stronger for lupus anticoagulant than with the other 2 antibodies, with different studies³⁴ finding an odds ratio ranging from 5 to 16. A positive lupus anticoagulant test with or without a moderate to high titer of anticardiolipin or anti-beta-2GPI IgM or IgG constitutes a high-risk profile, while a moderate to high titer of anticardiolipin or anti-beta-2GPI IgM or IgG constitutes a moderate-risk profile. A low titer of anticardiolipin or anti-beta-2GPI IgM or IgG constitutes a low-risk profile that may not be associated with thrombosis.³⁵

Antiphospholipid syndrome is important to recognize because of the need for long-term anticoagulation to prevent recurrence.³⁶ It may be primary, when it occurs on its own, or secondary, when it occurs in association with another autoimmune disease such as lupus.

Venous events in antiphospholipid syndrome most commonly manifest as lower-limb deep vein thrombosis or pulmonary embolism, while arterial events most commonly manifest as stroke or transient ischemic attack.³⁷ Obstetric manifestations may include not only miscarriage and stillbirth, but also preterm delivery, intrauterine growth retardation, and preeclampsia, all occurring due to placental insufficiency.

The frequency of antiphospholipid antibodies has been estimated as 13.5% in patients with stroke, 11% with myocardial infarction, 9.5% with deep vein thrombosis, and 6% for those with pregnancy morbidity.³⁸

Some noncriteria manifestations have also been recognized in antiphospholipid syndrome, such as thrombocytopenia, cardiac vegetations (Libman-Sachs endocarditis), livedo reticularis, and nephropathy.

The indications for antiphospholipid antibody testing are listed in Table 4.²⁹ For the patient described in the vignette, it would be appropriate to test for antiphospholipid antibodies because of her unprovoked thrombosis, thrombocytopenia, and prolonged aPTT. Anticoagulant treatment is known to be associated with false-positive lupus anticoagulant, so any blood samples should be drawn before such treatment is commenced.

Back to our patient

Our patient’s anticardiolipin IgG test is negative, while her lupus anticoagulant and beta-2GPI IgG are positive. She has no clinical or laboratory features suggesting lupus.

She is started on warfarin. After 3 months, the warfarin is interrupted for several days, and she is retested for all 3 antiphospholipid antibodies. Her beta-2GPI I IgG and lupus anticoagulant tests are again positive. Because of the persistent antiphospholipid antibody positivity and clinical history of deep vein thrombosis, her condition is diagnosed as primary antiphospholipid syndrome. She is advised to continue anticoagulant therapy indefinitely.

 

 

ANTINEUTROPHIL CYTOPLASMIC ANTIBODY

A 34-year-old man who is an injecting drug user presents with a 2-week history of fever, malaise, and generalized arthralgia. There are no localizing symptoms of infection. Notable findings on examination include a temperature of 38.0°C (100.4°F), needle track marks in his arms, nonblanching vasculitic rash in his legs, and a systolic murmur over the precordium.

His white blood cell count is 15.3 × 10⁹/L (reference range 3.7–11.0), and his C-reactive protein level is 234 mg/dL (normal < 3). Otherwise, results of blood cell counts, liver enzyme tests, renal function tests, urinalysis, and chest radiography are normal.

Two sets of blood cultures are drawn. Transthoracic echocardiography and the antineutrophil cytoplasmic antibody (ANCA) test are requested, as are screening tests for human immunodeficiency virus, hepatitis B, and hepatitis C.

Was the ANCA test indicated in this patient?

ANCAs are autoantibodies against antigens located in the cytoplasmic granules of neutrophils and monocytes. They are associated with small-vessel vasculitides such as granulomatosis with polyangiitis (GPA), microscopic polyangiitis (MPA), eosinophilic granulomatosis with polyangiitis (EGPA), and isolated pauciimmune crescentic glomerulonephritis, all collectively known as ANCA-associated vasculitis (AAV).³⁹

Laboratory methods to detect ANCA include indirect immunofluorescence and antigen-specific enzyme immunoassays. Indirect immunofluorescence only tells us whether or not an antibody that is targeting a cytoplasmic antigen is present. Based on the indirect immunofluorescent pattern, ANCA can be classified as follows:

• Perinuclear or p-ANCA (if the targeted antigen is located just around the nucleus and extends into it)
• Cytoplasmic or c-ANCA (if the targeted antigen is located farther away from the nucleus)
• Atypical ANCA (if the indirect immunofluorescent pattern does not fit with either p-ANCA or c-ANCA).

Indirect immunofluorescence does not give information about the exact antigen that is targeted; this can only be obtained by performing 1 of the antigen-specific immunoassays. The target antigen for c-ANCA is usually proteinase-3 (PR3), while that for p-ANCA could be myeloperoxidase (MPO), cathepsin, lysozyme, lactoferrin, or bactericidal permeability inhibitor. Anti-PR3 is highly specific for GPA, while anti-MPO is usually associated with MPA and EGPA. Less commonly, anti-PR3 may be seen in patients with MPA and anti-MPO in those with GPA. Hence, there is an increasing trend toward classifying ANCA-associated vasculitis into PR3-associated or MPO-associated vasculitis rather than as GPA, MPA, EGPA, or renal-limited vasculitis.⁴⁰

Several audits have shown that the ANCA test is widely misused and requested indiscriminately to rule out vasculitis. This results in a lower positive predictive value, possible harm to patients due to increased false-positive rates, and increased burden on the laboratory.^41–43 At least 2 separate groups have demonstrated that a gating policy that refuses ANCA testing in patients without clinical evidence of systemic vasculitis can reduce the number of inappropriate requests, improve the diagnostic yield, and make it more clinically relevant and cost-effective.^44,45

The clinician should bear in mind that:

ANCA testing should be requested only if the pretest probability of ANCA-associated vasculitis is high. The indications proposed by the International Consensus Statement on ANCA testing⁴⁶ are listed in Table 5. These criteria have been clinically validated, with 1 study even demonstrating that no cases of ANCA-associated vasculitis would be missed if these guidelines are followed.⁴⁷

Current guidelines recommend using one of the antigen-specific assays for PR3 and MPO as the primary screening method.⁴⁸ Until recently, indirect immunofluorescence was used to screen for ANCA-associated vasculitis, and positive results were confirmed by ELISA to detect ANCAs specific for PR3 and MPO,⁴⁹ but this is no longer recommended because of recent evidence suggesting a large variability between the different indirect immunofluorescent methods and improved diagnostic performance of the antigen-specific assays.

In a large multicenter study by Damoiseaux et al, the specificity with the different antigen-specific immunoassays was 98% to 99% for PR3-ANCA and 96% to 99% for MPO-ANCA.⁵⁰

ANCA-associated vasculitis should not be considered excluded if the PR3 and MPO-ANCA are negative. In the Damoiseaux study, about 11% to 15% of patients with GPA and 8% to 24% of patients with MPA tested negative for both PR3 and MPO-ANCA.⁵⁰

If the ANCA result is negative and clinical suspicion for ANCA-associated vasculitis is high, the clinician may wish to consider requesting another immunoassay method or indirect immunofluorescence. Results of indirect immunofluorescent testing results may be positive in those with a negative immunoassay, and vice versa.

A positive ANCA result is not diagnostic of ANCA-associated vasculitis. Numerous other conditions are associated with ANCA, usually p-ANCA or atypical ANCA (Table 6). The antigens targeted by these ANCAs are usually cathepsin, lysozyme, lactoferrin, and bactericidal permeability inhibitor.

Thus, the ANCA result should always be interpreted in the context of the whole clinical picture.⁵¹ Biopsy should still be considered the gold standard for the diagnosis of ANCA-associated vasculitis. The ANCA titer can help to improve clinical interpretation, because the likelihood of ANCA-associated vasculitis increases with higher levels of PR3 and MPO-ANCA.⁵²

Back to our patient

Our patient’s blood cultures grow methicillin-sensitive Staphylococcus aureus in both sets after 48 hours. Transthoracic echocardiography reveals vegetations around the tricuspid valve, with no evidence of valvular regurgitation. The diagnosis is right-sided infective endocarditis. He is started on appropriate antibiotics.

Tests for human immunodeficiency virus, hepatitis B, and hepatitis C are negative. The ANCA test is positive for MPO-ANCA at 28 IU/mL (normal < 10).

The positive ANCA is thought to be related to the infective endocarditis. His vasculitis is most likely secondary to infective endocarditis and not ANCA-associated vasculitis. The ANCA test need not have been requested in the first place.

 

 

HUMAN LEUKOCYTE ANTIGEN-B27

A 22-year-old man presents to his primary care physician with a 4-month history of gradually worsening low back pain associated with early morning stiffness lasting more than 2 hours. He has no peripheral joint symptoms.

In the last 2 years, he has had 2 separate episodes of uveitis. There is a family history of ankylosing spondylitis in his father. Examination reveals global restriction of lumbar movements but is otherwise unremarkable. Magnetic resonance imaging (MRI) of the lumbar spine and sacroiliac joints is normal.

Should this patient be tested for human leukocyte antigen-B27 (HLA-B27)?

The major histocompatibility complex (MHC) is a gene complex that is present in all animals. It encodes proteins that help with immunologic tolerance. HLA simply refers to the human version of the MHC.⁵³ The HLA gene complex, located on chromosome 6, is categorized into class I, class II, and class III. HLA-B is one of the 3 class I genes. Thus, a positive HLA-B27 result simply means that the particular gene is present in that person.

HLA-B27 is strongly associated with ankylosing spondylitis, also known as axial spondyloarthropathy.⁵⁴ Other genes also contribute to the pathogenesis of ankylosing spondylitis, but HLA-B27 is present in more than 90% of patients with this disease and is by far considered the most important. The association is not as strong for peripheral spondyloarthropathy, with studies reporting a frequency of up to 75% for reactive arthritis and inflammatory bowel disease-associated arthritis, and up to 50% for psoriatic arthritis and uveitis.⁵⁵

About 9% of healthy, asymptomatic individuals may have HLA-B27, so the mere presence of this gene is not evidence of disease.⁵⁶ There may be up to a 20-fold increased risk of ankylosing spondylitis among those who are HLA-B27-positive.⁵⁷

Some HLA genes have many different alleles, each of which is given a number (explaining the number 27 that follows the B). Closely related alleles that differ from one another by only a few amino-acid substitutions are then categorized together, thus accounting for more than 100 subtypes of HLA-B27 (designated from HLA-B*2701 to HLA-B*27106). These subtypes vary in frequency among different racial groups, and the population prevalence of ankylosing spondylitis parallels the frequency of HLA-B27.⁵⁸ The most common subtype seen in white people and American Indians is B*2705. HLA-B27 is rare in blacks, explaining the rarity of ankylosing spondylitis in this population. Further examples include HLA-B*2704, which is seen in Asians, and HLA-B*2702, seen in Mediterranean populations. Not all subtypes of HLA-B27 are associated with disease, and some, like HLA-B*2706, may also be protective.

When should the clinician consider testing for HLA-B27?

Not all patients with low back pain need an HLA-B27 test. First, it is important to look for clinical features of axial spondyloarthropathy (Table 7). The unifying feature of spondyloarthropathy is enthesitis (inflammation at the sites of insertion of tendons or ligaments on the skeleton). Inflammation of axial entheses causes spondylitis and sacroiliitis, manifesting as inflammatory back pain. Clinical clues to inflammatory back pain include insidious onset, aggravation with rest or inactivity, prolonged early morning stiffness, disturbed sleep during the second half of the night, relief with movement or activity, alternating gluteal pain (due to sacroiliitis), and good response to anti-inflammatory medication (although nonspecific).

Peripheral spondyloarthropathy may present with arthritis, enthesitis (eg, heel pain due to inflammation at the site of insertion of the Achilles tendon or plantar fascia), or dactylitis (“sausage” swelling of the whole finger or toe due to extension of inflammation beyond the margins of the joint). Other clues may include psoriasis, inflammatory bowel disease, history of preceding gastrointestinal or genitourinary infection, family history of similar conditions, and history of recurrent uveitis.

For the initial assessment of patients who have inflammatory back pain, plain radiography of the sacroiliac joints is considered the gold standard.⁵⁹ If plain radiography does not show evidence of sacroiliitis, MRI of the sacroiliac joints should be considered. While plain radiography can reveal only structural changes such as sclerosis, erosions, and ankylosis, MRI is useful to evaluate for early inflammatory changes such as bone marrow edema. Imaging the lumbar spine is not necessary, as the sacroiliac joints are almost invariably involved in axial spondyloarthropathy, and lesions seldom occur in the lumbar spine in isolation.⁶⁰

The diagnosis of ankylosing spondylitis previously relied on confirmatory imaging features, but based on the new International Society classification criteria,^61–63 which can be applied to patients with more than 3 months of back pain and age of onset of symptoms before age 45, patients can be classified as having 1 of the following:

• Radiographic axial spondyloarthropathy, if they have evidence of sacroiliitis on imaging plus 1 other feature of spondyloarthropathy
• Nonradiographic axial spondyloarthropathy, if they have a positive HLA-B27 plus 2 other features of spondyloarthropathy (Table 7).

These new criteria have a sensitivity of 82.9% and specificity of 84.4%.^62,63 The disease burden of radiographic and nonradiographic axial spondyloarthropathy has been shown to be similar, suggesting that they are part of the same disease spectrum. Thus, the HLA-B27 test is useful to make a diagnosis of axial spondyloarthropathy even in the absence of imaging features and could be requested in patients with 2 or more features of spondyloarthropathy. In the absence of imaging features and a negative HLA-B27 result, however, the patient cannot be classified as having axial spondyloarthropathy.

Back to our patient

The absence of radiographic evidence would not exclude axial spondyloarthropathy in our patient. The HLA-B27 test is requested because of the inflammatory back pain and the presence of 2 spondyloarthropathy features (uveitis and the family history) and is reported to be positive. His disease is classified as nonradiographic axial spondyloarthropathy.

He is started on regular naproxen and is referred to a physiotherapist. After 1 month, he reports significant symptomatic improvement. He asks if he can be retested for HLA-B27 to see if it has become negative. We tell him that there is no point in repeating it, as it is a gene and will not disappear.

SUMMARY: CONSIDER THE CLINICAL PICTURE

When approaching a patient suspected of having a rheumatologic disease, a clinician should first consider the clinical presentation and the intended purpose of each test. The tests, in general, might serve several purposes. They might help to:

Increase the likelihood of the diagnosis in question. For example, a positive rheumatoid factor or anticitrullinated peptide antibody can help diagnose rheumatoid arthritis in a patient with early polyarthritis, a positive HLA-B27 can help diagnose ankylosing spondylitis in patients with inflammatory back pain and normal imaging, and a positive ANCA can help diagnose ANCA-associated vasculitis in a patient with glomerulonephritis.

Reduce the likelihood of the diagnosis in question. For example, a negative antinuclear antibody test reduces the likelihood of lupus in a patient with joint pains.

Monitor the condition. For example DNA antibodies can be used to monitor the activity of lupus.

Plan the treatment strategy. For example, one might consider lifelong anticoagulation if antiphospholipid antibodies are persistently positive in a patient with thrombosis.

Prognosticate. For example, positive rheumatoid factor and anticitrullinated peptide antibody increase the risk of erosive rheumatoid arthritis.

If the test was requested in the absence of a clear indication and the result is positive, it is important to bear in mind the potential pitfalls associated with that test and not attach a diagnostic label prematurely. None of the tests can confirm or exclude a condition, so the results should always be interpreted in the context of the whole clinical picture.   

This issue of the Journal includes 3 articles related to clinical testing. Each focuses on a different content area of clinical medicine and each has a different higher arching message.

May et al discuss one of the most common laboratory tests we order, the complete blood cell count, and how to interpret and unlock additional information that we often overlook.

Singh et al explain the utility and limitations of assessing hepatic fibrosis in patients with known liver disease using specialized and increasingly available imaging techniques in patients with common diseases that may progress to liver failure.

Using several clinical scenarios, Suresh explores the limitations of serologic testing in patients with a potential “autoimmune” or systemic inflammatory syndrome (which, based on new consultations I see in my rheumatology clinic, seems to be virtually everyone who has experienced pain or fatigue).

The Journal also continues our ongoing series on Smart Testing that has focused on tests and testing strategies that have a strong evidence basis to support or discourage their utilization in specific settings. But in most real-life clinical scenarios, relatively little directly applicable evidence can be brought to bear on our decision process with a specific patient. Hence the ongoing need for each of us to refine our clinical reasoning skills, and to recognize the continuing challenges facing the incorporation of artificial intelligence and algorithmic practice into the management of the individual patient sitting or lying in front of us.

The challenge is to balance input from Watson, “Dr. Google,” our accumulated anecdotal and group experience, and specific data from the patient’s physical examination and provided history. All these sources are valuable, and I believe that how we thoughtfully and purposefully weigh and incorporate this information into practice defines us as the clinicians we are.

This issue of the Journal includes 3 articles related to clinical testing. Each focuses on a different content area of clinical medicine and each has a different higher arching message.

May et al discuss one of the most common laboratory tests we order, the complete blood cell count, and how to interpret and unlock additional information that we often overlook.

Singh et al explain the utility and limitations of assessing hepatic fibrosis in patients with known liver disease using specialized and increasingly available imaging techniques in patients with common diseases that may progress to liver failure.

Using several clinical scenarios, Suresh explores the limitations of serologic testing in patients with a potential “autoimmune” or systemic inflammatory syndrome (which, based on new consultations I see in my rheumatology clinic, seems to be virtually everyone who has experienced pain or fatigue).

The Journal also continues our ongoing series on Smart Testing that has focused on tests and testing strategies that have a strong evidence basis to support or discourage their utilization in specific settings. But in most real-life clinical scenarios, relatively little directly applicable evidence can be brought to bear on our decision process with a specific patient. Hence the ongoing need for each of us to refine our clinical reasoning skills, and to recognize the continuing challenges facing the incorporation of artificial intelligence and algorithmic practice into the management of the individual patient sitting or lying in front of us.

The challenge is to balance input from Watson, “Dr. Google,” our accumulated anecdotal and group experience, and specific data from the patient’s physical examination and provided history. All these sources are valuable, and I believe that how we thoughtfully and purposefully weigh and incorporate this information into practice defines us as the clinicians we are.

This issue of the Journal includes 3 articles related to clinical testing. Each focuses on a different content area of clinical medicine and each has a different higher arching message.

May et al discuss one of the most common laboratory tests we order, the complete blood cell count, and how to interpret and unlock additional information that we often overlook.

Singh et al explain the utility and limitations of assessing hepatic fibrosis in patients with known liver disease using specialized and increasingly available imaging techniques in patients with common diseases that may progress to liver failure.

Using several clinical scenarios, Suresh explores the limitations of serologic testing in patients with a potential “autoimmune” or systemic inflammatory syndrome (which, based on new consultations I see in my rheumatology clinic, seems to be virtually everyone who has experienced pain or fatigue).

The Journal also continues our ongoing series on Smart Testing that has focused on tests and testing strategies that have a strong evidence basis to support or discourage their utilization in specific settings. But in most real-life clinical scenarios, relatively little directly applicable evidence can be brought to bear on our decision process with a specific patient. Hence the ongoing need for each of us to refine our clinical reasoning skills, and to recognize the continuing challenges facing the incorporation of artificial intelligence and algorithmic practice into the management of the individual patient sitting or lying in front of us.

The challenge is to balance input from Watson, “Dr. Google,” our accumulated anecdotal and group experience, and specific data from the patient’s physical examination and provided history. All these sources are valuable, and I believe that how we thoughtfully and purposefully weigh and incorporate this information into practice defines us as the clinicians we are.

A 62-year-old woman presented to our emergency department with fever, chills, hoarseness, pain on swallowing, and a painful neck. Her symptoms had begun 1 day earlier. Because acetaminophen brought no improvement, she went to an urgent care facility, where a nasal swab polymerase chain reaction test was positive for influenza A, and a throat swab rapid test was positive for group A streptococci. She was then referred to our emergency department.

She reported no pre-existing conditions predisposing her to infection. Her temperature was 99.9°F (37.7°C), pulse 112 beats per minute, and respiratory rate 24 breaths per minute. The physical examination was unremarkable except for bilateral anterior cervical adenopathy and bilateral anterior neck tenderness. Her pharynx was not injected, and no exudate, palatal edema, or petechiae were noted.

Results of initial laboratory testing were as follows:

• White blood cell count 20.5 × 10⁹/L (reference range 3.9–11)
• Neutrophils 76% (42%–75%)
• Bands 15% (0%–5%)
• Lymphocytes 3% (21%–51%)
• Erythrocyte sedimentation rate 75 mm/h (< 20 mm/h)
• C-reactive protein 247.14 mg/L (≤ 3 mg/L)
• Serum aminotransferase levels were normal.
• Polymerase chain reaction testing of a nasal swab was negative for viral infection.

Throat swabs and blood samples were sent for culture.

Laryngoscopy revealed a normal oropharynx, hypopharynx, and larynx, but an erythematous and edematous epiglottis with postcricoid edema. Lateral radiography of the neck revealed an enlarged epiglottis (Figure 1).

She was started on ceftriaxone 1 g intravenously every 24 hours, with close observation in the medical intensive care unit, where she was admitted because of epiglottitis. On hospital day 3, the throat culture was reported as negative, but the blood culture was reported as positive for Haemophilus influenzae. Thus, the clinical diagnosis was acute epiglottitis due to H influenzae, not group A streptococci.

The patient completed 10 days of ceftriaxone therapy; her recovery was uneventful, and she was discharged on hospital day 10.

INFLUENZA: CHALLENGES TO PROMPT, ACCURATE DIAGNOSIS

During influenza season, emergency departments are inundated with adults with influenza A and other viral respiratory infections. This makes prompt, accurate diagnosis a challenge,¹ given the broad differential diagnosis.^2,3 Adults with influenza and its complications as well as unrelated conditions can present a special challenge.⁴

Our patient presented with acute-onset influenza A and was then found to have acute epiglottitis, an unexpected complication of influenza A.⁵ A positive rapid test for group A streptococci done at an urgent care facility led emergency department physicians to assume that the acute epiglottitis was due to group A streptococci. Unless correlated with clinical findings, results of rapid diagnostic tests may mislead the unwary practitioner. Accurate diagnosis should be based mainly on the history and physical findings. Results of rapid diagnostic tests can be helpful if interpreted in the clinical context.^6–8

The rapid test for streptococci is appropriate for the diagnosis of pharyngitis due to group A streptococci in people under age 30 with acute-onset sore throat, fever, and bilateral acute cervical adenopathy, without fatigue or myalgias. However, the rapid test does not differentiate colonization from infection. Group A streptococci are common colonizers with viral pharyngitis. In 30% of cases of Epstein-Barr virus pharyngitis, there is colonization with group A streptococci. A positive rapid test in such cases can result in the wrong diagnosis, ie, pharyngitis due to group A streptococci rather than Epstein-Barr virus.

A 62-year-old woman presented to our emergency department with fever, chills, hoarseness, pain on swallowing, and a painful neck. Her symptoms had begun 1 day earlier. Because acetaminophen brought no improvement, she went to an urgent care facility, where a nasal swab polymerase chain reaction test was positive for influenza A, and a throat swab rapid test was positive for group A streptococci. She was then referred to our emergency department.

She reported no pre-existing conditions predisposing her to infection. Her temperature was 99.9°F (37.7°C), pulse 112 beats per minute, and respiratory rate 24 breaths per minute. The physical examination was unremarkable except for bilateral anterior cervical adenopathy and bilateral anterior neck tenderness. Her pharynx was not injected, and no exudate, palatal edema, or petechiae were noted.

Results of initial laboratory testing were as follows:

• White blood cell count 20.5 × 10⁹/L (reference range 3.9–11)
• Neutrophils 76% (42%–75%)
• Bands 15% (0%–5%)
• Lymphocytes 3% (21%–51%)
• Erythrocyte sedimentation rate 75 mm/h (< 20 mm/h)
• C-reactive protein 247.14 mg/L (≤ 3 mg/L)
• Serum aminotransferase levels were normal.
• Polymerase chain reaction testing of a nasal swab was negative for viral infection.

Throat swabs and blood samples were sent for culture.

Laryngoscopy revealed a normal oropharynx, hypopharynx, and larynx, but an erythematous and edematous epiglottis with postcricoid edema. Lateral radiography of the neck revealed an enlarged epiglottis (Figure 1).

She was started on ceftriaxone 1 g intravenously every 24 hours, with close observation in the medical intensive care unit, where she was admitted because of epiglottitis. On hospital day 3, the throat culture was reported as negative, but the blood culture was reported as positive for Haemophilus influenzae. Thus, the clinical diagnosis was acute epiglottitis due to H influenzae, not group A streptococci.

The patient completed 10 days of ceftriaxone therapy; her recovery was uneventful, and she was discharged on hospital day 10.

INFLUENZA: CHALLENGES TO PROMPT, ACCURATE DIAGNOSIS

During influenza season, emergency departments are inundated with adults with influenza A and other viral respiratory infections. This makes prompt, accurate diagnosis a challenge,¹ given the broad differential diagnosis.^2,3 Adults with influenza and its complications as well as unrelated conditions can present a special challenge.⁴

Our patient presented with acute-onset influenza A and was then found to have acute epiglottitis, an unexpected complication of influenza A.⁵ A positive rapid test for group A streptococci done at an urgent care facility led emergency department physicians to assume that the acute epiglottitis was due to group A streptococci. Unless correlated with clinical findings, results of rapid diagnostic tests may mislead the unwary practitioner. Accurate diagnosis should be based mainly on the history and physical findings. Results of rapid diagnostic tests can be helpful if interpreted in the clinical context.^6–8

The rapid test for streptococci is appropriate for the diagnosis of pharyngitis due to group A streptococci in people under age 30 with acute-onset sore throat, fever, and bilateral acute cervical adenopathy, without fatigue or myalgias. However, the rapid test does not differentiate colonization from infection. Group A streptococci are common colonizers with viral pharyngitis. In 30% of cases of Epstein-Barr virus pharyngitis, there is colonization with group A streptococci. A positive rapid test in such cases can result in the wrong diagnosis, ie, pharyngitis due to group A streptococci rather than Epstein-Barr virus.

A 62-year-old woman presented to our emergency department with fever, chills, hoarseness, pain on swallowing, and a painful neck. Her symptoms had begun 1 day earlier. Because acetaminophen brought no improvement, she went to an urgent care facility, where a nasal swab polymerase chain reaction test was positive for influenza A, and a throat swab rapid test was positive for group A streptococci. She was then referred to our emergency department.

She reported no pre-existing conditions predisposing her to infection. Her temperature was 99.9°F (37.7°C), pulse 112 beats per minute, and respiratory rate 24 breaths per minute. The physical examination was unremarkable except for bilateral anterior cervical adenopathy and bilateral anterior neck tenderness. Her pharynx was not injected, and no exudate, palatal edema, or petechiae were noted.

Results of initial laboratory testing were as follows:

• White blood cell count 20.5 × 10⁹/L (reference range 3.9–11)
• Neutrophils 76% (42%–75%)
• Bands 15% (0%–5%)
• Lymphocytes 3% (21%–51%)
• Erythrocyte sedimentation rate 75 mm/h (< 20 mm/h)
• C-reactive protein 247.14 mg/L (≤ 3 mg/L)
• Serum aminotransferase levels were normal.
• Polymerase chain reaction testing of a nasal swab was negative for viral infection.

Throat swabs and blood samples were sent for culture.

Laryngoscopy revealed a normal oropharynx, hypopharynx, and larynx, but an erythematous and edematous epiglottis with postcricoid edema. Lateral radiography of the neck revealed an enlarged epiglottis (Figure 1).

She was started on ceftriaxone 1 g intravenously every 24 hours, with close observation in the medical intensive care unit, where she was admitted because of epiglottitis. On hospital day 3, the throat culture was reported as negative, but the blood culture was reported as positive for Haemophilus influenzae. Thus, the clinical diagnosis was acute epiglottitis due to H influenzae, not group A streptococci.

The patient completed 10 days of ceftriaxone therapy; her recovery was uneventful, and she was discharged on hospital day 10.

INFLUENZA: CHALLENGES TO PROMPT, ACCURATE DIAGNOSIS

During influenza season, emergency departments are inundated with adults with influenza A and other viral respiratory infections. This makes prompt, accurate diagnosis a challenge,¹ given the broad differential diagnosis.^2,3 Adults with influenza and its complications as well as unrelated conditions can present a special challenge.⁴

Our patient presented with acute-onset influenza A and was then found to have acute epiglottitis, an unexpected complication of influenza A.⁵ A positive rapid test for group A streptococci done at an urgent care facility led emergency department physicians to assume that the acute epiglottitis was due to group A streptococci. Unless correlated with clinical findings, results of rapid diagnostic tests may mislead the unwary practitioner. Accurate diagnosis should be based mainly on the history and physical findings. Results of rapid diagnostic tests can be helpful if interpreted in the clinical context.^6–8

The rapid test for streptococci is appropriate for the diagnosis of pharyngitis due to group A streptococci in people under age 30 with acute-onset sore throat, fever, and bilateral acute cervical adenopathy, without fatigue or myalgias. However, the rapid test does not differentiate colonization from infection. Group A streptococci are common colonizers with viral pharyngitis. In 30% of cases of Epstein-Barr virus pharyngitis, there is colonization with group A streptococci. A positive rapid test in such cases can result in the wrong diagnosis, ie, pharyngitis due to group A streptococci rather than Epstein-Barr virus.

A bedridden 78-year-old man with advanced dementia was transported to the dermatology outpatient department with a rash and intense itching over the entire body from the feet to the scalp. His medical history included diabetes mellitus, hypertension, and Alzheimer dementia. He had no history of allergies.

His vital signs were normal. Physical examination noted widespread crusted hyperkeratotic lesions on the trunk, arms, and hands (Figure 1). A potassium hydroxide mount of scrapings of the lesions revealed extensive infestation with Sarcoptes scabiei,1 with a very high number of eggs and fecal pellets (Figure 2). This finding led to a diagnosis of crusted or Norwegian scabies, an extremely contagious form of scabies seen in immunocompromised, malnourished, and bedridden elderly or institutionalized patients.

DIAGNOSIS, TREATMENT, CONTROL

The differential diagnosis of Norwegian scabies includes psoriasis, eczema, contact dermatitis, insect bites, seborrheic dermatitis, lichen planus, systemic infection, palmoplantar keratoderma, and cutaneous lymphoma.²

Treatment involves eradicating the infestation with a topical ointment consisting of permethrin, crotamiton, lindane, benzyl benzoate, and sulfur, applied directly to the skin. However, topical treatments often cannot penetrate the crusted and thickened skin, leading to treatment failure. A dose of oral ivermectin 200 µg/kg on days 1, 2, and 8 is a safe, effective, first-line treatment for Norwegian scabies, rapidly reducing scabies symptoms.³ Adverse effects of oral ivermectin are rare and usually minor.

Norwegian scabies is extremely contagious, spread by close physical contact and sharing of contaminated items such as clothing, bedding, towels, and furniture. Scabies mites can survive off the skin for 48 to 72 hours at room temperature.⁴ Potentially contaminated items should be decontaminated by washing in hot water and drying in a drying machine or by dry cleaning. Body contact with other contaminated items should be avoided for at least 72 hours.

Outbreaks can spread among patients, visitors, and medical staff in institutions such as nursing homes, day care centers, long-term-care facilities, and hospitals.⁵ Early identification facilitates appropriate management and treatment, thereby preventing infection and community-wide scabies outbreaks.          

Acknowledgment: The authors would like to sincerely thank Paul Williams for his editing of the article.

A bedridden 78-year-old man with advanced dementia was transported to the dermatology outpatient department with a rash and intense itching over the entire body from the feet to the scalp. His medical history included diabetes mellitus, hypertension, and Alzheimer dementia. He had no history of allergies.

His vital signs were normal. Physical examination noted widespread crusted hyperkeratotic lesions on the trunk, arms, and hands (Figure 1). A potassium hydroxide mount of scrapings of the lesions revealed extensive infestation with Sarcoptes scabiei,1 with a very high number of eggs and fecal pellets (Figure 2). This finding led to a diagnosis of crusted or Norwegian scabies, an extremely contagious form of scabies seen in immunocompromised, malnourished, and bedridden elderly or institutionalized patients.

DIAGNOSIS, TREATMENT, CONTROL

The differential diagnosis of Norwegian scabies includes psoriasis, eczema, contact dermatitis, insect bites, seborrheic dermatitis, lichen planus, systemic infection, palmoplantar keratoderma, and cutaneous lymphoma.²

Treatment involves eradicating the infestation with a topical ointment consisting of permethrin, crotamiton, lindane, benzyl benzoate, and sulfur, applied directly to the skin. However, topical treatments often cannot penetrate the crusted and thickened skin, leading to treatment failure. A dose of oral ivermectin 200 µg/kg on days 1, 2, and 8 is a safe, effective, first-line treatment for Norwegian scabies, rapidly reducing scabies symptoms.³ Adverse effects of oral ivermectin are rare and usually minor.

Norwegian scabies is extremely contagious, spread by close physical contact and sharing of contaminated items such as clothing, bedding, towels, and furniture. Scabies mites can survive off the skin for 48 to 72 hours at room temperature.⁴ Potentially contaminated items should be decontaminated by washing in hot water and drying in a drying machine or by dry cleaning. Body contact with other contaminated items should be avoided for at least 72 hours.

Outbreaks can spread among patients, visitors, and medical staff in institutions such as nursing homes, day care centers, long-term-care facilities, and hospitals.⁵ Early identification facilitates appropriate management and treatment, thereby preventing infection and community-wide scabies outbreaks.          

Acknowledgment: The authors would like to sincerely thank Paul Williams for his editing of the article.

A bedridden 78-year-old man with advanced dementia was transported to the dermatology outpatient department with a rash and intense itching over the entire body from the feet to the scalp. His medical history included diabetes mellitus, hypertension, and Alzheimer dementia. He had no history of allergies.

His vital signs were normal. Physical examination noted widespread crusted hyperkeratotic lesions on the trunk, arms, and hands (Figure 1). A potassium hydroxide mount of scrapings of the lesions revealed extensive infestation with Sarcoptes scabiei,1 with a very high number of eggs and fecal pellets (Figure 2). This finding led to a diagnosis of crusted or Norwegian scabies, an extremely contagious form of scabies seen in immunocompromised, malnourished, and bedridden elderly or institutionalized patients.

DIAGNOSIS, TREATMENT, CONTROL

The differential diagnosis of Norwegian scabies includes psoriasis, eczema, contact dermatitis, insect bites, seborrheic dermatitis, lichen planus, systemic infection, palmoplantar keratoderma, and cutaneous lymphoma.²

Treatment involves eradicating the infestation with a topical ointment consisting of permethrin, crotamiton, lindane, benzyl benzoate, and sulfur, applied directly to the skin. However, topical treatments often cannot penetrate the crusted and thickened skin, leading to treatment failure. A dose of oral ivermectin 200 µg/kg on days 1, 2, and 8 is a safe, effective, first-line treatment for Norwegian scabies, rapidly reducing scabies symptoms.³ Adverse effects of oral ivermectin are rare and usually minor.

Norwegian scabies is extremely contagious, spread by close physical contact and sharing of contaminated items such as clothing, bedding, towels, and furniture. Scabies mites can survive off the skin for 48 to 72 hours at room temperature.⁴ Potentially contaminated items should be decontaminated by washing in hot water and drying in a drying machine or by dry cleaning. Body contact with other contaminated items should be avoided for at least 72 hours.

Outbreaks can spread among patients, visitors, and medical staff in institutions such as nursing homes, day care centers, long-term-care facilities, and hospitals.⁵ Early identification facilitates appropriate management and treatment, thereby preventing infection and community-wide scabies outbreaks.          

Acknowledgment: The authors would like to sincerely thank Paul Williams for his editing of the article.

No. The early repolarization pattern on electrocardiography (ECG) in asymp­tomatic patients is nearly always a benign incidental finding. However, in a patient with a history of idiopathic ventricular fibrillation or a family history of sudden cardiac death, the finding warrants further evaluation.

DEFINING EARLY REPOLARIZATION

Published studies differ in their definitions of the early repolarization pattern. In 2016, Patton et al described it as ST-segment elevation in the absence of chest pain, with terminal QRS slur or terminal QRS notch.¹ However, Mcfarlane et al² described it as a J-point elevation of at least 0.1 mV in 2 or more contiguous leads on 12-lead ECG, excluding leads V₁ to V₃, with the presence of terminal QRS notch or slur and QRS duration less than 120 msec. They defined the J point as either the peak of QRS notch or the beginning of QRS slur (Figure 1).² J-point elevation and QRS notch or slur are most commonly seen in left lateral leads and less often in inferior leads.

The early repolarization pattern may mimic patterns seen in myocardial infarction, pericarditis, ventricular aneurysm, hyperkalemia, and hypothermia,^1,3 and misinterpreting the pattern can lead to unnecessary laboratory testing, imaging, medication use, and hospital admissions. On the other hand, misinterpreting it as benign in the presence of certain features of the history or clinical presentation can delay the diagnosis and treatment of a potentially critical condition.

PREVALENCE AND MECHANISMS

The prevalence of the early repolarization pattern in the general population ranges from 5% to 15%; the wide range reflects differences in the definition, as well as variability in the pattern of early repolarization over time.⁴

The early repolarization pattern is more commonly seen in African American men and in young, physically active individuals.³ In one study, it was observed in 15% of cases of idiopathic ventricular fibrillation and sudden cardiac death, especially in people ages 35 to 45.⁴ While there is evidence of a heritable basis in the general population, a family history of early repolarization is not known to increase the risk of sudden cardiac death.

A proposed mechanism for the early repolarization pattern is an imbalance in the ion channel system, resulting in variable refractoriness of multiple myocardial regions and varying excitability in the myocardium. This can produce a voltage gradient between myocardial regions, which is believed to cause the major hallmarks of the early repolarization pattern, ie, ST-segment elevation and QRS notching or slurring.³

Although the mechanistic basis of ventricular arrhythmia in patients with early repolarization is still incompletely understood, certain associations may help define the ECG phenotype that suggests increased risk of sudden cardiac death (Table 1).

MANAGEMENT

The early repolarization pattern is nearly always a benign incidental finding on ECG, with no specific signs or symptoms attributed to it. High-risk features on ECG are associated with a modest increase in absolute risk of sudden cardiac death and warrant clinical correlation.

In the absence of syncope or family history of sudden cardiac death, early repolarization does not merit further workup.²

In patients with a history of unexplained syncope and a family history of sudden cardiac death, early repolarization should be considered in overall risk stratification.¹ Early repolarization in a patient with previous idiopathic ventricular fibrillation warrants referral for electrophysiologic study and, if indicated, insertion of an implantable cardiac defibrillator for secondary prevention.⁵

No. The early repolarization pattern on electrocardiography (ECG) in asymp­tomatic patients is nearly always a benign incidental finding. However, in a patient with a history of idiopathic ventricular fibrillation or a family history of sudden cardiac death, the finding warrants further evaluation.

DEFINING EARLY REPOLARIZATION

Published studies differ in their definitions of the early repolarization pattern. In 2016, Patton et al described it as ST-segment elevation in the absence of chest pain, with terminal QRS slur or terminal QRS notch.¹ However, Mcfarlane et al² described it as a J-point elevation of at least 0.1 mV in 2 or more contiguous leads on 12-lead ECG, excluding leads V₁ to V₃, with the presence of terminal QRS notch or slur and QRS duration less than 120 msec. They defined the J point as either the peak of QRS notch or the beginning of QRS slur (Figure 1).² J-point elevation and QRS notch or slur are most commonly seen in left lateral leads and less often in inferior leads.

The early repolarization pattern may mimic patterns seen in myocardial infarction, pericarditis, ventricular aneurysm, hyperkalemia, and hypothermia,^1,3 and misinterpreting the pattern can lead to unnecessary laboratory testing, imaging, medication use, and hospital admissions. On the other hand, misinterpreting it as benign in the presence of certain features of the history or clinical presentation can delay the diagnosis and treatment of a potentially critical condition.

PREVALENCE AND MECHANISMS

The prevalence of the early repolarization pattern in the general population ranges from 5% to 15%; the wide range reflects differences in the definition, as well as variability in the pattern of early repolarization over time.⁴

The early repolarization pattern is more commonly seen in African American men and in young, physically active individuals.³ In one study, it was observed in 15% of cases of idiopathic ventricular fibrillation and sudden cardiac death, especially in people ages 35 to 45.⁴ While there is evidence of a heritable basis in the general population, a family history of early repolarization is not known to increase the risk of sudden cardiac death.

A proposed mechanism for the early repolarization pattern is an imbalance in the ion channel system, resulting in variable refractoriness of multiple myocardial regions and varying excitability in the myocardium. This can produce a voltage gradient between myocardial regions, which is believed to cause the major hallmarks of the early repolarization pattern, ie, ST-segment elevation and QRS notching or slurring.³

Although the mechanistic basis of ventricular arrhythmia in patients with early repolarization is still incompletely understood, certain associations may help define the ECG phenotype that suggests increased risk of sudden cardiac death (Table 1).

MANAGEMENT

The early repolarization pattern is nearly always a benign incidental finding on ECG, with no specific signs or symptoms attributed to it. High-risk features on ECG are associated with a modest increase in absolute risk of sudden cardiac death and warrant clinical correlation.

In the absence of syncope or family history of sudden cardiac death, early repolarization does not merit further workup.²

In patients with a history of unexplained syncope and a family history of sudden cardiac death, early repolarization should be considered in overall risk stratification.¹ Early repolarization in a patient with previous idiopathic ventricular fibrillation warrants referral for electrophysiologic study and, if indicated, insertion of an implantable cardiac defibrillator for secondary prevention.⁵

No. The early repolarization pattern on electrocardiography (ECG) in asymp­tomatic patients is nearly always a benign incidental finding. However, in a patient with a history of idiopathic ventricular fibrillation or a family history of sudden cardiac death, the finding warrants further evaluation.

DEFINING EARLY REPOLARIZATION

Published studies differ in their definitions of the early repolarization pattern. In 2016, Patton et al described it as ST-segment elevation in the absence of chest pain, with terminal QRS slur or terminal QRS notch.¹ However, Mcfarlane et al² described it as a J-point elevation of at least 0.1 mV in 2 or more contiguous leads on 12-lead ECG, excluding leads V₁ to V₃, with the presence of terminal QRS notch or slur and QRS duration less than 120 msec. They defined the J point as either the peak of QRS notch or the beginning of QRS slur (Figure 1).² J-point elevation and QRS notch or slur are most commonly seen in left lateral leads and less often in inferior leads.

The early repolarization pattern may mimic patterns seen in myocardial infarction, pericarditis, ventricular aneurysm, hyperkalemia, and hypothermia,^1,3 and misinterpreting the pattern can lead to unnecessary laboratory testing, imaging, medication use, and hospital admissions. On the other hand, misinterpreting it as benign in the presence of certain features of the history or clinical presentation can delay the diagnosis and treatment of a potentially critical condition.

PREVALENCE AND MECHANISMS

The prevalence of the early repolarization pattern in the general population ranges from 5% to 15%; the wide range reflects differences in the definition, as well as variability in the pattern of early repolarization over time.⁴

The early repolarization pattern is more commonly seen in African American men and in young, physically active individuals.³ In one study, it was observed in 15% of cases of idiopathic ventricular fibrillation and sudden cardiac death, especially in people ages 35 to 45.⁴ While there is evidence of a heritable basis in the general population, a family history of early repolarization is not known to increase the risk of sudden cardiac death.

A proposed mechanism for the early repolarization pattern is an imbalance in the ion channel system, resulting in variable refractoriness of multiple myocardial regions and varying excitability in the myocardium. This can produce a voltage gradient between myocardial regions, which is believed to cause the major hallmarks of the early repolarization pattern, ie, ST-segment elevation and QRS notching or slurring.³

Although the mechanistic basis of ventricular arrhythmia in patients with early repolarization is still incompletely understood, certain associations may help define the ECG phenotype that suggests increased risk of sudden cardiac death (Table 1).

MANAGEMENT

The early repolarization pattern is nearly always a benign incidental finding on ECG, with no specific signs or symptoms attributed to it. High-risk features on ECG are associated with a modest increase in absolute risk of sudden cardiac death and warrant clinical correlation.

In the absence of syncope or family history of sudden cardiac death, early repolarization does not merit further workup.²

In patients with a history of unexplained syncope and a family history of sudden cardiac death, early repolarization should be considered in overall risk stratification.¹ Early repolarization in a patient with previous idiopathic ventricular fibrillation warrants referral for electrophysiologic study and, if indicated, insertion of an implantable cardiac defibrillator for secondary prevention.⁵

NOTE: The scenario presented here is partly based on cases reported elsewhere by Martínez-Valles et al¹ and Fernández-Rodríguez et al.²

A 55-year-old man is admitted to the hospital with generalized malaise, paresthesias, and severe hypertension. He says he had experienced agitation along with weakness on exertion 24 hours before presentation to the emergency department, with subsequent onset of paresthesias in his lower extremities and perioral area.

He is already known to have mild chronic obstructive pulmonary disease, with a ratio of forced expiratory volume in 1 second (FEV₁)to forced vital capacity (FVC) of less than 70% and an FEV₁ 85% of predicted. In addition, he was recently diagnosed with diabetes, resistant hypertension requiring maximum doses of 3 agents (a calcium channel blocker, an angiotensin-converting enzyme inhibitor, and a loop diuretic), and hyperlipidemia.

He is a current smoker with a 30-pack-year smoking history. He does not use alcohol. His family history is noncontributory.

His blood pressure is 190/110 mm Hg despite adherence to his 3-drug regimen. His oxygen saturation is 94% on room air, respiratory rate in the low 30s, and pulse 110 beats/minute. He has normal breath sounds, normal S1 and S2 with an S4 gallop, bilateral lower-extremity edema, truncal obesity, and abdominal striae. Electrocardiography shows tachycardia with first-degree atrioventicular block. Chest radiography shows an opacity in the right middle lung field. Initial laboratory results and those from 1 year ago are shown in Table 1.

ASSESSING ACID-BASE DISORDERS

1. What type of acid-base disorder does this patient have?

• Metabolic acidosis
• Respiratory acidosis
• Metabolic alkalosis
• Respiratory alkalosis

The patient has metabolic alkalosis.

A 5-step approach

If a patient has an acid-base disorder, one should use a 5-step process to characterize it (Table 2).³

1. Acidosis or alkalosis? The patient’s arterial pH is 7.5, which is alkalemic because it is higher than 7.44.

2. Metabolic or respiratory? The primary process in our patient is overwhelmingly metabolic, as his partial pressure of carbon dioxide (Pco₂) is slightly elevated, a direction that would cause acidosis, not alkalosis.

3. The anion gap (the serum sodium concentration minus the sum of the chloride and bicarbonate concentrations) is normal at 8 mmol/L (DRG:HYBRiD-XL Immunoassay and Clinical Chemistry Analyzer, reference range 8–16).

4. Is the disturbance compensated? We have determined that this patient has a metabolic alkalemia; the question now is whether there is any compensation for the primary disturbance.

In metabolic alkalosis, the Pco₂ may increase by approximately 0.6 mm Hg (range 0.5–0.8) above the nominal normal level of 40 mm Hg for each 1-mmol/L increase in bicarbonate above the nominal normal level of 25 mmol/L.⁴ If the patient requires oxygen, the calculation may be unreliable, however, as hypoxemia may have an overriding influence on respiratory drive.

Patients with chronically high Pco₂ levels such as those with chronic obstructive pulmonary disease can become accustomed to high carbon dioxide levels and lose their hyper-
capnic respiratory drive. Giving oxygen supplementation is thought to decrease respiratory drive in these patients, so that they will breathe slower and retain more carbon dioxide. There is some degree of respiratory compensation for metabolic alkalosis that occurs by breathing less, though it is limited overall—even in very alkalotic patients, breathing less results in CO₂ retention, which, by displacing O₂ molecules in the alveoli, will in turn result in hypoxia. The brain then senses the hypoxia and makes one breathe faster, thereby limiting this compensation. 

This patient’s serum bicarbonate level is 40 mmol/L, or 15 mmol/L higher than the nominal normal level. If he is compensating, his Pco₂ should be 40 + (15 × 0.6) = 49 mm Hg, and in fact it is 51 mm Hg, which is within the normal range of expected compensation (47.5–52 mm Hg). Therefore, yes, he is compensating for the primary disturbance.  

5. In metabolic acidosis, is there a delta gap? As our patient has metabolic alkalosis, not acidosis, this question does not apply in this case.

 

 

WHICH TEST TO FIND THE CAUSE?

2. Which is the best test to order next to determine the cause of this patient’s hypokalemic metabolic alkalosis?

• Serum magnesium level
• Spot urine chloride
• Renal ultrasonography
• 24-hour urine collection for sodium, potassium, and chloride

The first step in the algorithm for hypokalemic metabolic alkalosis (Figure 1) is to obtain a spot urine chloride measurement. If this value is low, the hypokalemic metabolic alkalosis is volume-responsive; if it is high, the disturbance is volume-independent.

The patient’s loop diuretic is withheld for 12 hours and a spot urine chloride is obtained, which is reported as 44 mmol/L. This high value suggests that a volume-independent hypo­kalemic metabolic alkalosis is present with potassium depletion.

As for the other answer choices:

Serum magnesium. Though hypomagnesemia can cause hypokalemia due to lack of inhibition of renal outer medullary potassium channels and subsequent increased excretion of potassium in the apical tubular membrane, it is not independently associated with acid-base disturbances.⁵

Renal ultrasonography gives information about structural kidney disease but is of limited utility in identifying the cause of hypokalemic metabolic alkalosis.

A 24-hour urine collection is unnecessary in this setting and would ultimately result in delay in diagnosis, as spot urine chloride is a more efficient means of rapidly distinguishing volume-responsive vs volume-independent causes of hypokalemic metabolic alkalosis.⁶

IS HIS HYPERTENSION SECONDARY? IF SO, WHAT IS THE CAUSE?

Several features of this case suggest that the patient’s hypertension is secondary rather than primary. It is of recent onset. The patient’s family history is noncontributory, and his hypertension is resistant to the use of maximum doses of 3 antihypertensive agents.

3. Which of the following causes of secondary hypertension is not commonly associated with hypokalemia and metabolic alkalosis?

• Hyperaldosteronism
• Liddle syndrome
• Cushing syndrome
• Renal parenchymal disease
• Chronic licorice ingestion

Renal parenchymal disease is a cause of resistant hypertension, but it is not characterized by metabolic alkalosis, hypokalemia, and  elevated urine chloride,⁷ while the others listed here—hyperaldosteronism, Liddle syndrome, Cushing syndrome, and chronic licorice ingestion­—are. Other common causes of resistant hypertension without these metabolic abnormalities include obstructive sleep apnea, alcohol abuse, and nonadherence to treatment.

While treatment of hypertension with loop diuretics can result in hypokalemia and metabolic alkalosis due to the effect of these drugs on potassium reabsorption in the loop of Henle, the patient’s hypokalemia persisted after this agent was withdrawn.⁸

Causes of hypokalemic metabolic alkalosis with and without hypertension are further delineated in Figure 1.

Additional diagnostic testing: Plasma renin and plasma aldosterone

At this juncture, the differential diagnosis for this patient’s potassium depletion, metabolic alkalosis, high urine chloride, and hypertension has been narrowed to primary or secondary hyperaldosteronism, surreptitious mineralocorticoid ingestion, Cushing syndrome, licorice ingestion, Liddle syndrome, or one of the 3 hydroxylase deficiencies (11-, 17-, and 21-) (Figure 1).

Although clues in the history, physical examination, and imaging may suggest a specific cause of his abnormal laboratory values, the next step in the diagnostic workup is to measure the plasma renin and aldosterone levels (Table 3).

 

HYPERALDOSTERONISM

4. Hyperaldosteronism is associated with which of the following patterns of renin and aldosterone values?

• High renin, high aldosterone, normal ratio of plasma aldosterone concentration (PAC) to plasma renin activity (PRA)
• Low renin, low aldosterone, normal PAC–PRA ratio
• Low renin, high aldosterone, high PAC–PRA ratio
• High renin, low aldosterone, low PAC–PRA ratio

The pattern of low renin, high aldosterone, and high PAC–PRA ratio is associated with hyperaldosteronism.

Primary hyperaldosteronism

Primary hyperaldosteronism is one of the most common causes of resistant hypertension and is underappreciated, being diagnosed in up to 20% of patients referred to hypertension specialty clinics.⁷ Potassium levels may be normal, likely contributing to its lack of recognition in this target population.

Primary hyperaldosteronism should be suspected in patients who have a plasma aldosterone PAC–PRA ratio greater than 20 with elevated plasma aldosterone concentrations
(> 15 ng/dL).

Persistently elevated aldosterone levels in the setting of elevated plasma volume is proof that aldosterone secretion is independent of the renin-angiotensin-aldosterone axis, and therefore is autonomous (secondary to adrenal tumor or hyperplasia). Further testing in the form of oral salt loading, saline infusion, or fludrocortisone (a sodium-retaining steroid) administration is thus required to confirm inappropriate, autonomous aldosterone secretion.⁹

After establishing the diagnosis of primary hyperaldosteronism, one should determine the subtype (ie, due to an adrenal carcinoma, unilateral hypersecreting adenoma, or unilateral or bilateral hyperplasia). Further testing includes adrenal computed tomography (CT) to rule out adrenal carcinomas, which are suspected with adenomas larger than 4 cm. Though part of the diagnostic workup, CT as a means of confirmational testing alone does not preclude the possibility of bilateral adrenal hyperplasia in some patients, even in the presence of an adrenal adenoma. For this reason, adrenal venous sampling is required to definitively determine whether the condition is due to a hypersecreting adrenal adenoma or unilateral or bilateral hyperplasia.^9,10

Treatment of primary hyperaldosteronism depends on the subtype of the disease and involves salt restriction in addition to an aldosterone antagonist (spironolactone or eplerenone in the case of bilateral disease) or surgery (unilateral disease).^9,11,12

Secondary hyperaldosteronism

Secondary hyperaldosteronism should be suspected when plasma renin and aldosterone levels are both elevated with a PAC–PRA ratio less than 10.

This pattern is most commonly seen with diuretic use but can also be a consequence of renal artery stenosis or, rarely, a renin-secreting tumor.¹³ Renal artery stenosis is a common finding in patients with hypertension undergoing cardiac catheterization, which is not surprising as more than 90% of such stenoses are atherosclerotic.⁷ Renin-secreting tumors are exceedingly rare, with fewer than 100 cases reported in the literature, and are more common in younger individuals.¹³

Our patient has low-normal aldosterone and plasma renin

On further testing, this patient’s plasma aldosterone level is 2.55 ng/dL (normal < 15 ng/dL), his plasma renin activity is 0.53 ng/mL/hour (normal 0.2–2.8 ng/mL/hour), and his PAC–PRA ratio is therefore 4.81.

The categories discussed thus far have included primary and secondary hyperaldosteronism, which typically do not present with low to normal levels of both renin and aldosterone. Surreptitious mineralocorticoid use could present in this manner, but is unlikely in this patient, whose medications do not include fludrocortisone.

The low-normal values thus lead to consideration of a third category: apparent mineralocorticoid excess. Diseases in this category such as Cushing disease or adrenocorticotropic hormone (ACTH) excess are characterized by increases in corticosteroids so that the potassium depletion, metabolic alkalosis, and hypertension are not a consequence of renin and aldosterone but rather the excess corticosteroids.¹⁴

Causes of apparent mineralocorticoid excess

There are several possible causes of mineralocorticoid excess associated with hypertension and hypokalemic metabolic alkalosis not due to renin and aldosterone.

Chronic licorice ingestion in high volumes is one such cause and is thought to result in inhibition of 11B-hydroxysteroid dehydrogenase or possibly cortisol oxidase by licorice’s active component, glycyrrhetinic acid. This inhibition results in an inability to convert cortisol to cortisone. The cortisol excess binds to mineralocorticoid receptors, and acting like aldosterone, results in hypertension and hypokalemic metabolic alkalosis as well as feedback inhibition of renin and aldosterone levels.¹⁵

Partial hydroxylase deficiencies, though rare, should also be considered as a cause of hypokalemic metabolic alkalosis, hypertension, and, potentially, hirsutism and clitoromegaly in women. They can be diagnosed with elevated levels of 17-ketosteroids and dehydroepiandrosterone sulfate, both of which, in excess, may act on aldosterone receptors in a manner similar to cortisol.¹⁶

Liddle syndrome, a rare autosomal dominant condition, may also present with suppressed levels of both renin and aldosterone. In contrast to the disorders of nonaldosterone mineralocorticoid excess, however, the sodium channel defect in Liddle syndrome is characterized by a primary increase in sodium reabsorption in the collecting tubule and potassium wasting. The resultant volume expansion leads to suppressed renin and aldosterone levels and hypertension with low potassium and elevated bicarbonate concentrations.¹⁷

Liddle syndrome is commonly diagnosed in childhood but may go unrecognized due to occasional absence of hypokalemia at presentation. Potassium-sparing diuretics such as amiloride or triamterene are the mainstays of treatment.¹⁸

Hypercortisolism results in hypokalemic metabolic alkalosis through the effect of excess cortisol on mineralocorticoid receptors, similar to what occurs in chronic licorice ingestion. Under normal conditions, 11B-hydroxysteroid dehydrogenase converts cortisol to cortisone and is the rate-limiting step in the mineralocorticoid action of cortisol. When plasma cortisol levels are in excess, however, the enzyme is saturated so that its action is insufficient, resulting in cortisol binding to mineralocorticoid receptors to produce effects similar to that of aldosterone on acid-base and electrolyte balance and blood pressure.¹⁹

The increase in blood pressure that is associated with elevated plasma levels of cortisol is not attributable solely to its effect on mineralocorticoid receptors, however. The pathogenesis is multifactorial and not fully understood, but it also is thought to involve increased peripheral vascular sensitivity to adrenergic agonists, increased hepatic production of angiotensinogen, as well as direct and indirect cardiotoxic effects via metabolic and electrolyte aberrations.²⁰ Other common effects and manifestations of hypercortisolism are listed in Table 4.

Rates of cardiovascular and all-cause mortality are increased in patients with long-term hypercortisolism, even after plasma concentrations of cortisol are normalized.²¹

Figure 2 shows the cascade of the hypothalamic-pituitary-adrenal axis.

 

 

TESTING FOR HYPERCORTISOLISM IN OUR PATIENT

Given the patient’s clinical presentation and laboratory and imaging findings with normal plasma renin and aldosterone levels, a workup for suspected hypercortisolism is initiated.

Initial diagnostic testing for hypercortisolism depends on the degree of clinical suspicion. In those with low probability of the disease, testing should consist of 1 of the following, as a single negative test may be sufficient to rule out the disease:

• 24-hour urinary cortisol levels
• Overnight dexamethasone suppression testing
• Late-night salivary cortisol measurements.

In those with a high index of suspicion, 2 of the aforementioned tests should be performed, as 1 normal result may not be sufficient to exclude the diagnosis.^22,23

A 24-hour urinary cortisol collection and overnight dexamethasone suppression test are obtained. His 24-hour urinary free cortisol level is elevated at 6,600 µg (normal 4–100), and suppression testing with 8 mg of dexamethasone (a form of “high-dose” testing)demonstrates only an 8% decline in serum cortisol levels. Cortisol should generally drop more than 90%.

Morning serum cortisol concentration is less than 5 µg/dL (140 nmol/L) in most patients with Cushing disease (ie, a pituitary tumor), and is usually undetectable in normal subjects. Only about 50% of neuroendocrine ACTH-secreting tumors will suppress with this test.

The patient’s clinical presentation, in conjunction with his diagnostic testing, are thus consistent with Cushing syndrome.

CUSHING SYNDROME

Cushing syndrome is most often exogenous or iatrogenic, ie, a result of supraphysiologic doses of glucocorticoids used to treat a variety of inflammatory, autoimmune, and neoplastic conditions.

Endogenous Cushing syndrome, on the other hand, is rare, with an estimated prevalence of 0.7 to 2.4 cases per million per year. ACTH-dependent causes account for 80% of endogenous Cushing syndrome cases, with ACTH-secreting pituitary adenomas (Cushing disease) accounting for 75% to 80% and ectopic ACTH secretion accounting for 15% to 20%. Less than 1% of cases are due to tumors that produce corticotropin-releasing hormone (CRH).

ACTH-independent Cushing syndrome is diagnosed in 20% of endogenous cases and is most commonly caused by a unilateral adrenal tumor. Rare causes of ACTH-independent disease include adrenal carcinoma, McCune-Albright syndrome, and adrenal hyperplasia.²⁴

The patient’s ACTH is high

To determine whether this is an ACTH-dependent or independent process, the next step is to order an ACTH level. His ACTH level is high at 107 pg/mL (normal < 46 pg/mL), confirming the diagnosis of ACTH-dependent Cushing syndrome.

To find out if this ACTH-dependent process is due to a pituitary adenoma, magnetic resonance imaging (MRI) of the pituitary is obtained but is normal.

Large masses (> 6 mm) strongly suggest Cushing disease, but these tumors are often small and may be missed even with more advanced imaging techniques. Corticotropin-secreting adenomas arising from normal cells in the pituitary retain some sensitivity to glucocorticoid negative feedback and CRH stimulation, and thus high-dose dexamethasone suppression testing in conjunction with CRH stimulation testing can be used to differentiate Cushing disease from ectopic ACTH secretion.^24,25 Both of these tests have poor diagnostic accuracy, however, and thus inferior petrosal sampling remains the gold standard for the diagnosis of Cushing disease.

Given this patient’s history of smoking and a right hilar pulmonary opacity on chest radiography, inferior petrosal sampling was deferred in favor of CT of the chest, which showed a right consolidative lung lesion (Figure 3). Subsequent CT-guided fine-needle biopsy demonstrated a small-cell carcinoma.

ACTH-SECRETING TUMORS

5. Cushing syndrome due to ectopic ACTH secretion is most commonly attributed to which of the following tumors?

• Small-cell lung carcinoma
• Pancreatic carcinoma
• Medullary thyroid carcinoma
• Gastrinoma

Severe cases of Cushing syndrome are often attributable to ectopic ACTH secretion due to an underlying malignancy, most commonly small-cell lung carcinoma or neuroendocrine tumors of pulmonary origin. Other causes include pancreatic and thymic neuroendocrine tumors, gastrinomas, and medullary thyroid carcinoma.^25,26

Because most ACTH-producing tumors are intrathoracic, initial imaging in cases of suspected ectopic ACTH secretion should focus on the chest, with CT the usual first choice. Octreotide scintigraphy can also be useful in localizing disease, as many neuroendocrine tumors express somatostatin receptors. Specialized positron-emission tomography scans may also be helpful in tumor identification.²⁴

 

 

TREATMENT OF CUSHING SYNDROME DUE TO ECTOPIC ACTH SECRETION

6. Which of the following is most appropriate medical therapy for suppression of cortisol secretion in Cushing syndrome due to ectopic ACTH secretion?

• Spironolactone
• Dexamethasone
• Somatostatin
• Estrogen
• Ketoconazole

Hyperglycemia, hypokalemia, hypertension, psychiatric disturbances, venous thromboembolism, and systemic infections appear to be common in ectopic ACTH syndrome and often correlate with the degree of hypercortisolemia. Severe Cushing syndrome due to ectopic ACTH secretion is an emergency requiring prompt control of cortisol secretion.

First-line treatments include steroidogenesis inhibitors (ketoconazole, metyrapone, etomidate, mitotane) and glucocorticoid receptor antagonists (mifepristone). High-dose spironolactone and eplerenone can also be used to treat the hypertension and hypokalemia associated with mineralocorticoid receptor stimulation. Definitive treatment involves surgical resection, chemotherapy, or radiotherapy when applicable.^24,25

After confirmation of the diagnosis, the patient is prescribed ketoconazole and spironolactone, with substantial improvement. He subsequently is started on combination chemotherapy and radiation therapy for his small-cell lung carcinoma.

DISCUSSION

The differential diagnosis for hypokalemia is broad and relies on information obtained during the history and physical examination, followed by interpretation of selected laboratory results. Myriad pathologies in diverse organ systems, eg, diarrhea, renal tubular acidosis, and adrenal disease, may be responsible for a low serum potassium. Further categorizing potassium depletion on the basis of an associated acid-base disturbance, such as metabolic alkalosis, allows one to use an algorithmic approach that can identify specific etiologies responsible for both the potassium and the acid-base disturbances.

Using the spot urine chloride in the setting of hypokalemic metabolic alkalosis with or without hypertension can narrow the differential diagnosis and allow additional clinical findings to guide clinical problem-solving and decision-making, even for conditions not commonly encountered in routine medical practice.

Obtaining renin and aldosterone measurements in patients with potassium depletion, metabolic alkalosis, high urine chloride excretion, and hypertension permits further categorization into 3 clinical groups: elevated aldosterone and renin (secondary hyperaldosteronism), elevated aldosterone and low renin (primary hyperaldosteronism), or apparent mineralocorticoid excess wherein neither renin nor aldosterone are responsible for the syndrome.

The patient in our case had apparent mineralocorticoid excess as a consequence of an ACTH-producing small-cell carcinoma.

NOTE: The scenario presented here is partly based on cases reported elsewhere by Martínez-Valles et al¹ and Fernández-Rodríguez et al.²

A 55-year-old man is admitted to the hospital with generalized malaise, paresthesias, and severe hypertension. He says he had experienced agitation along with weakness on exertion 24 hours before presentation to the emergency department, with subsequent onset of paresthesias in his lower extremities and perioral area.

He is already known to have mild chronic obstructive pulmonary disease, with a ratio of forced expiratory volume in 1 second (FEV₁)to forced vital capacity (FVC) of less than 70% and an FEV₁ 85% of predicted. In addition, he was recently diagnosed with diabetes, resistant hypertension requiring maximum doses of 3 agents (a calcium channel blocker, an angiotensin-converting enzyme inhibitor, and a loop diuretic), and hyperlipidemia.

He is a current smoker with a 30-pack-year smoking history. He does not use alcohol. His family history is noncontributory.

His blood pressure is 190/110 mm Hg despite adherence to his 3-drug regimen. His oxygen saturation is 94% on room air, respiratory rate in the low 30s, and pulse 110 beats/minute. He has normal breath sounds, normal S1 and S2 with an S4 gallop, bilateral lower-extremity edema, truncal obesity, and abdominal striae. Electrocardiography shows tachycardia with first-degree atrioventicular block. Chest radiography shows an opacity in the right middle lung field. Initial laboratory results and those from 1 year ago are shown in Table 1.

ASSESSING ACID-BASE DISORDERS

1. What type of acid-base disorder does this patient have?

• Metabolic acidosis
• Respiratory acidosis
• Metabolic alkalosis
• Respiratory alkalosis

The patient has metabolic alkalosis.

A 5-step approach

If a patient has an acid-base disorder, one should use a 5-step process to characterize it (Table 2).³

1. Acidosis or alkalosis? The patient’s arterial pH is 7.5, which is alkalemic because it is higher than 7.44.

2. Metabolic or respiratory? The primary process in our patient is overwhelmingly metabolic, as his partial pressure of carbon dioxide (Pco₂) is slightly elevated, a direction that would cause acidosis, not alkalosis.

3. The anion gap (the serum sodium concentration minus the sum of the chloride and bicarbonate concentrations) is normal at 8 mmol/L (DRG:HYBRiD-XL Immunoassay and Clinical Chemistry Analyzer, reference range 8–16).

4. Is the disturbance compensated? We have determined that this patient has a metabolic alkalemia; the question now is whether there is any compensation for the primary disturbance.

In metabolic alkalosis, the Pco₂ may increase by approximately 0.6 mm Hg (range 0.5–0.8) above the nominal normal level of 40 mm Hg for each 1-mmol/L increase in bicarbonate above the nominal normal level of 25 mmol/L.⁴ If the patient requires oxygen, the calculation may be unreliable, however, as hypoxemia may have an overriding influence on respiratory drive.

Patients with chronically high Pco₂ levels such as those with chronic obstructive pulmonary disease can become accustomed to high carbon dioxide levels and lose their hyper-
capnic respiratory drive. Giving oxygen supplementation is thought to decrease respiratory drive in these patients, so that they will breathe slower and retain more carbon dioxide. There is some degree of respiratory compensation for metabolic alkalosis that occurs by breathing less, though it is limited overall—even in very alkalotic patients, breathing less results in CO₂ retention, which, by displacing O₂ molecules in the alveoli, will in turn result in hypoxia. The brain then senses the hypoxia and makes one breathe faster, thereby limiting this compensation. 

This patient’s serum bicarbonate level is 40 mmol/L, or 15 mmol/L higher than the nominal normal level. If he is compensating, his Pco₂ should be 40 + (15 × 0.6) = 49 mm Hg, and in fact it is 51 mm Hg, which is within the normal range of expected compensation (47.5–52 mm Hg). Therefore, yes, he is compensating for the primary disturbance.  

5. In metabolic acidosis, is there a delta gap? As our patient has metabolic alkalosis, not acidosis, this question does not apply in this case.

 

 

WHICH TEST TO FIND THE CAUSE?

2. Which is the best test to order next to determine the cause of this patient’s hypokalemic metabolic alkalosis?

• Serum magnesium level
• Spot urine chloride
• Renal ultrasonography
• 24-hour urine collection for sodium, potassium, and chloride

The first step in the algorithm for hypokalemic metabolic alkalosis (Figure 1) is to obtain a spot urine chloride measurement. If this value is low, the hypokalemic metabolic alkalosis is volume-responsive; if it is high, the disturbance is volume-independent.

The patient’s loop diuretic is withheld for 12 hours and a spot urine chloride is obtained, which is reported as 44 mmol/L. This high value suggests that a volume-independent hypo­kalemic metabolic alkalosis is present with potassium depletion.

As for the other answer choices:

Serum magnesium. Though hypomagnesemia can cause hypokalemia due to lack of inhibition of renal outer medullary potassium channels and subsequent increased excretion of potassium in the apical tubular membrane, it is not independently associated with acid-base disturbances.⁵

Renal ultrasonography gives information about structural kidney disease but is of limited utility in identifying the cause of hypokalemic metabolic alkalosis.

A 24-hour urine collection is unnecessary in this setting and would ultimately result in delay in diagnosis, as spot urine chloride is a more efficient means of rapidly distinguishing volume-responsive vs volume-independent causes of hypokalemic metabolic alkalosis.⁶

IS HIS HYPERTENSION SECONDARY? IF SO, WHAT IS THE CAUSE?

Several features of this case suggest that the patient’s hypertension is secondary rather than primary. It is of recent onset. The patient’s family history is noncontributory, and his hypertension is resistant to the use of maximum doses of 3 antihypertensive agents.

3. Which of the following causes of secondary hypertension is not commonly associated with hypokalemia and metabolic alkalosis?

• Hyperaldosteronism
• Liddle syndrome
• Cushing syndrome
• Renal parenchymal disease
• Chronic licorice ingestion

Renal parenchymal disease is a cause of resistant hypertension, but it is not characterized by metabolic alkalosis, hypokalemia, and  elevated urine chloride,⁷ while the others listed here—hyperaldosteronism, Liddle syndrome, Cushing syndrome, and chronic licorice ingestion­—are. Other common causes of resistant hypertension without these metabolic abnormalities include obstructive sleep apnea, alcohol abuse, and nonadherence to treatment.

While treatment of hypertension with loop diuretics can result in hypokalemia and metabolic alkalosis due to the effect of these drugs on potassium reabsorption in the loop of Henle, the patient’s hypokalemia persisted after this agent was withdrawn.⁸

Causes of hypokalemic metabolic alkalosis with and without hypertension are further delineated in Figure 1.

Additional diagnostic testing: Plasma renin and plasma aldosterone

At this juncture, the differential diagnosis for this patient’s potassium depletion, metabolic alkalosis, high urine chloride, and hypertension has been narrowed to primary or secondary hyperaldosteronism, surreptitious mineralocorticoid ingestion, Cushing syndrome, licorice ingestion, Liddle syndrome, or one of the 3 hydroxylase deficiencies (11-, 17-, and 21-) (Figure 1).

Although clues in the history, physical examination, and imaging may suggest a specific cause of his abnormal laboratory values, the next step in the diagnostic workup is to measure the plasma renin and aldosterone levels (Table 3).

 

HYPERALDOSTERONISM

4. Hyperaldosteronism is associated with which of the following patterns of renin and aldosterone values?

• High renin, high aldosterone, normal ratio of plasma aldosterone concentration (PAC) to plasma renin activity (PRA)
• Low renin, low aldosterone, normal PAC–PRA ratio
• Low renin, high aldosterone, high PAC–PRA ratio
• High renin, low aldosterone, low PAC–PRA ratio

The pattern of low renin, high aldosterone, and high PAC–PRA ratio is associated with hyperaldosteronism.

Primary hyperaldosteronism

Primary hyperaldosteronism is one of the most common causes of resistant hypertension and is underappreciated, being diagnosed in up to 20% of patients referred to hypertension specialty clinics.⁷ Potassium levels may be normal, likely contributing to its lack of recognition in this target population.

Primary hyperaldosteronism should be suspected in patients who have a plasma aldosterone PAC–PRA ratio greater than 20 with elevated plasma aldosterone concentrations
(> 15 ng/dL).

Persistently elevated aldosterone levels in the setting of elevated plasma volume is proof that aldosterone secretion is independent of the renin-angiotensin-aldosterone axis, and therefore is autonomous (secondary to adrenal tumor or hyperplasia). Further testing in the form of oral salt loading, saline infusion, or fludrocortisone (a sodium-retaining steroid) administration is thus required to confirm inappropriate, autonomous aldosterone secretion.⁹

After establishing the diagnosis of primary hyperaldosteronism, one should determine the subtype (ie, due to an adrenal carcinoma, unilateral hypersecreting adenoma, or unilateral or bilateral hyperplasia). Further testing includes adrenal computed tomography (CT) to rule out adrenal carcinomas, which are suspected with adenomas larger than 4 cm. Though part of the diagnostic workup, CT as a means of confirmational testing alone does not preclude the possibility of bilateral adrenal hyperplasia in some patients, even in the presence of an adrenal adenoma. For this reason, adrenal venous sampling is required to definitively determine whether the condition is due to a hypersecreting adrenal adenoma or unilateral or bilateral hyperplasia.^9,10

Treatment of primary hyperaldosteronism depends on the subtype of the disease and involves salt restriction in addition to an aldosterone antagonist (spironolactone or eplerenone in the case of bilateral disease) or surgery (unilateral disease).^9,11,12

Secondary hyperaldosteronism

Secondary hyperaldosteronism should be suspected when plasma renin and aldosterone levels are both elevated with a PAC–PRA ratio less than 10.

This pattern is most commonly seen with diuretic use but can also be a consequence of renal artery stenosis or, rarely, a renin-secreting tumor.¹³ Renal artery stenosis is a common finding in patients with hypertension undergoing cardiac catheterization, which is not surprising as more than 90% of such stenoses are atherosclerotic.⁷ Renin-secreting tumors are exceedingly rare, with fewer than 100 cases reported in the literature, and are more common in younger individuals.¹³

Our patient has low-normal aldosterone and plasma renin

On further testing, this patient’s plasma aldosterone level is 2.55 ng/dL (normal < 15 ng/dL), his plasma renin activity is 0.53 ng/mL/hour (normal 0.2–2.8 ng/mL/hour), and his PAC–PRA ratio is therefore 4.81.

The categories discussed thus far have included primary and secondary hyperaldosteronism, which typically do not present with low to normal levels of both renin and aldosterone. Surreptitious mineralocorticoid use could present in this manner, but is unlikely in this patient, whose medications do not include fludrocortisone.

The low-normal values thus lead to consideration of a third category: apparent mineralocorticoid excess. Diseases in this category such as Cushing disease or adrenocorticotropic hormone (ACTH) excess are characterized by increases in corticosteroids so that the potassium depletion, metabolic alkalosis, and hypertension are not a consequence of renin and aldosterone but rather the excess corticosteroids.¹⁴

Causes of apparent mineralocorticoid excess

There are several possible causes of mineralocorticoid excess associated with hypertension and hypokalemic metabolic alkalosis not due to renin and aldosterone.

Chronic licorice ingestion in high volumes is one such cause and is thought to result in inhibition of 11B-hydroxysteroid dehydrogenase or possibly cortisol oxidase by licorice’s active component, glycyrrhetinic acid. This inhibition results in an inability to convert cortisol to cortisone. The cortisol excess binds to mineralocorticoid receptors, and acting like aldosterone, results in hypertension and hypokalemic metabolic alkalosis as well as feedback inhibition of renin and aldosterone levels.¹⁵

Partial hydroxylase deficiencies, though rare, should also be considered as a cause of hypokalemic metabolic alkalosis, hypertension, and, potentially, hirsutism and clitoromegaly in women. They can be diagnosed with elevated levels of 17-ketosteroids and dehydroepiandrosterone sulfate, both of which, in excess, may act on aldosterone receptors in a manner similar to cortisol.¹⁶

Liddle syndrome, a rare autosomal dominant condition, may also present with suppressed levels of both renin and aldosterone. In contrast to the disorders of nonaldosterone mineralocorticoid excess, however, the sodium channel defect in Liddle syndrome is characterized by a primary increase in sodium reabsorption in the collecting tubule and potassium wasting. The resultant volume expansion leads to suppressed renin and aldosterone levels and hypertension with low potassium and elevated bicarbonate concentrations.¹⁷

Liddle syndrome is commonly diagnosed in childhood but may go unrecognized due to occasional absence of hypokalemia at presentation. Potassium-sparing diuretics such as amiloride or triamterene are the mainstays of treatment.¹⁸

Hypercortisolism results in hypokalemic metabolic alkalosis through the effect of excess cortisol on mineralocorticoid receptors, similar to what occurs in chronic licorice ingestion. Under normal conditions, 11B-hydroxysteroid dehydrogenase converts cortisol to cortisone and is the rate-limiting step in the mineralocorticoid action of cortisol. When plasma cortisol levels are in excess, however, the enzyme is saturated so that its action is insufficient, resulting in cortisol binding to mineralocorticoid receptors to produce effects similar to that of aldosterone on acid-base and electrolyte balance and blood pressure.¹⁹

The increase in blood pressure that is associated with elevated plasma levels of cortisol is not attributable solely to its effect on mineralocorticoid receptors, however. The pathogenesis is multifactorial and not fully understood, but it also is thought to involve increased peripheral vascular sensitivity to adrenergic agonists, increased hepatic production of angiotensinogen, as well as direct and indirect cardiotoxic effects via metabolic and electrolyte aberrations.²⁰ Other common effects and manifestations of hypercortisolism are listed in Table 4.

Rates of cardiovascular and all-cause mortality are increased in patients with long-term hypercortisolism, even after plasma concentrations of cortisol are normalized.²¹

Figure 2 shows the cascade of the hypothalamic-pituitary-adrenal axis.

 

 

TESTING FOR HYPERCORTISOLISM IN OUR PATIENT

Given the patient’s clinical presentation and laboratory and imaging findings with normal plasma renin and aldosterone levels, a workup for suspected hypercortisolism is initiated.

Initial diagnostic testing for hypercortisolism depends on the degree of clinical suspicion. In those with low probability of the disease, testing should consist of 1 of the following, as a single negative test may be sufficient to rule out the disease:

• 24-hour urinary cortisol levels
• Overnight dexamethasone suppression testing
• Late-night salivary cortisol measurements.

In those with a high index of suspicion, 2 of the aforementioned tests should be performed, as 1 normal result may not be sufficient to exclude the diagnosis.^22,23

A 24-hour urinary cortisol collection and overnight dexamethasone suppression test are obtained. His 24-hour urinary free cortisol level is elevated at 6,600 µg (normal 4–100), and suppression testing with 8 mg of dexamethasone (a form of “high-dose” testing)demonstrates only an 8% decline in serum cortisol levels. Cortisol should generally drop more than 90%.

Morning serum cortisol concentration is less than 5 µg/dL (140 nmol/L) in most patients with Cushing disease (ie, a pituitary tumor), and is usually undetectable in normal subjects. Only about 50% of neuroendocrine ACTH-secreting tumors will suppress with this test.

The patient’s clinical presentation, in conjunction with his diagnostic testing, are thus consistent with Cushing syndrome.

CUSHING SYNDROME

Cushing syndrome is most often exogenous or iatrogenic, ie, a result of supraphysiologic doses of glucocorticoids used to treat a variety of inflammatory, autoimmune, and neoplastic conditions.

Endogenous Cushing syndrome, on the other hand, is rare, with an estimated prevalence of 0.7 to 2.4 cases per million per year. ACTH-dependent causes account for 80% of endogenous Cushing syndrome cases, with ACTH-secreting pituitary adenomas (Cushing disease) accounting for 75% to 80% and ectopic ACTH secretion accounting for 15% to 20%. Less than 1% of cases are due to tumors that produce corticotropin-releasing hormone (CRH).

ACTH-independent Cushing syndrome is diagnosed in 20% of endogenous cases and is most commonly caused by a unilateral adrenal tumor. Rare causes of ACTH-independent disease include adrenal carcinoma, McCune-Albright syndrome, and adrenal hyperplasia.²⁴

The patient’s ACTH is high

To determine whether this is an ACTH-dependent or independent process, the next step is to order an ACTH level. His ACTH level is high at 107 pg/mL (normal < 46 pg/mL), confirming the diagnosis of ACTH-dependent Cushing syndrome.

To find out if this ACTH-dependent process is due to a pituitary adenoma, magnetic resonance imaging (MRI) of the pituitary is obtained but is normal.

Large masses (> 6 mm) strongly suggest Cushing disease, but these tumors are often small and may be missed even with more advanced imaging techniques. Corticotropin-secreting adenomas arising from normal cells in the pituitary retain some sensitivity to glucocorticoid negative feedback and CRH stimulation, and thus high-dose dexamethasone suppression testing in conjunction with CRH stimulation testing can be used to differentiate Cushing disease from ectopic ACTH secretion.^24,25 Both of these tests have poor diagnostic accuracy, however, and thus inferior petrosal sampling remains the gold standard for the diagnosis of Cushing disease.

Given this patient’s history of smoking and a right hilar pulmonary opacity on chest radiography, inferior petrosal sampling was deferred in favor of CT of the chest, which showed a right consolidative lung lesion (Figure 3). Subsequent CT-guided fine-needle biopsy demonstrated a small-cell carcinoma.

ACTH-SECRETING TUMORS

5. Cushing syndrome due to ectopic ACTH secretion is most commonly attributed to which of the following tumors?

• Small-cell lung carcinoma
• Pancreatic carcinoma
• Medullary thyroid carcinoma
• Gastrinoma

Severe cases of Cushing syndrome are often attributable to ectopic ACTH secretion due to an underlying malignancy, most commonly small-cell lung carcinoma or neuroendocrine tumors of pulmonary origin. Other causes include pancreatic and thymic neuroendocrine tumors, gastrinomas, and medullary thyroid carcinoma.^25,26

Because most ACTH-producing tumors are intrathoracic, initial imaging in cases of suspected ectopic ACTH secretion should focus on the chest, with CT the usual first choice. Octreotide scintigraphy can also be useful in localizing disease, as many neuroendocrine tumors express somatostatin receptors. Specialized positron-emission tomography scans may also be helpful in tumor identification.²⁴

 

 

TREATMENT OF CUSHING SYNDROME DUE TO ECTOPIC ACTH SECRETION

6. Which of the following is most appropriate medical therapy for suppression of cortisol secretion in Cushing syndrome due to ectopic ACTH secretion?

• Spironolactone
• Dexamethasone
• Somatostatin
• Estrogen
• Ketoconazole

Hyperglycemia, hypokalemia, hypertension, psychiatric disturbances, venous thromboembolism, and systemic infections appear to be common in ectopic ACTH syndrome and often correlate with the degree of hypercortisolemia. Severe Cushing syndrome due to ectopic ACTH secretion is an emergency requiring prompt control of cortisol secretion.

First-line treatments include steroidogenesis inhibitors (ketoconazole, metyrapone, etomidate, mitotane) and glucocorticoid receptor antagonists (mifepristone). High-dose spironolactone and eplerenone can also be used to treat the hypertension and hypokalemia associated with mineralocorticoid receptor stimulation. Definitive treatment involves surgical resection, chemotherapy, or radiotherapy when applicable.^24,25

After confirmation of the diagnosis, the patient is prescribed ketoconazole and spironolactone, with substantial improvement. He subsequently is started on combination chemotherapy and radiation therapy for his small-cell lung carcinoma.

DISCUSSION

The differential diagnosis for hypokalemia is broad and relies on information obtained during the history and physical examination, followed by interpretation of selected laboratory results. Myriad pathologies in diverse organ systems, eg, diarrhea, renal tubular acidosis, and adrenal disease, may be responsible for a low serum potassium. Further categorizing potassium depletion on the basis of an associated acid-base disturbance, such as metabolic alkalosis, allows one to use an algorithmic approach that can identify specific etiologies responsible for both the potassium and the acid-base disturbances.

Using the spot urine chloride in the setting of hypokalemic metabolic alkalosis with or without hypertension can narrow the differential diagnosis and allow additional clinical findings to guide clinical problem-solving and decision-making, even for conditions not commonly encountered in routine medical practice.

Obtaining renin and aldosterone measurements in patients with potassium depletion, metabolic alkalosis, high urine chloride excretion, and hypertension permits further categorization into 3 clinical groups: elevated aldosterone and renin (secondary hyperaldosteronism), elevated aldosterone and low renin (primary hyperaldosteronism), or apparent mineralocorticoid excess wherein neither renin nor aldosterone are responsible for the syndrome.

The patient in our case had apparent mineralocorticoid excess as a consequence of an ACTH-producing small-cell carcinoma.

NOTE: The scenario presented here is partly based on cases reported elsewhere by Martínez-Valles et al¹ and Fernández-Rodríguez et al.²

A 55-year-old man is admitted to the hospital with generalized malaise, paresthesias, and severe hypertension. He says he had experienced agitation along with weakness on exertion 24 hours before presentation to the emergency department, with subsequent onset of paresthesias in his lower extremities and perioral area.

He is already known to have mild chronic obstructive pulmonary disease, with a ratio of forced expiratory volume in 1 second (FEV₁)to forced vital capacity (FVC) of less than 70% and an FEV₁ 85% of predicted. In addition, he was recently diagnosed with diabetes, resistant hypertension requiring maximum doses of 3 agents (a calcium channel blocker, an angiotensin-converting enzyme inhibitor, and a loop diuretic), and hyperlipidemia.

He is a current smoker with a 30-pack-year smoking history. He does not use alcohol. His family history is noncontributory.

His blood pressure is 190/110 mm Hg despite adherence to his 3-drug regimen. His oxygen saturation is 94% on room air, respiratory rate in the low 30s, and pulse 110 beats/minute. He has normal breath sounds, normal S1 and S2 with an S4 gallop, bilateral lower-extremity edema, truncal obesity, and abdominal striae. Electrocardiography shows tachycardia with first-degree atrioventicular block. Chest radiography shows an opacity in the right middle lung field. Initial laboratory results and those from 1 year ago are shown in Table 1.

ASSESSING ACID-BASE DISORDERS

1. What type of acid-base disorder does this patient have?

• Metabolic acidosis
• Respiratory acidosis
• Metabolic alkalosis
• Respiratory alkalosis

The patient has metabolic alkalosis.

A 5-step approach

If a patient has an acid-base disorder, one should use a 5-step process to characterize it (Table 2).³

1. Acidosis or alkalosis? The patient’s arterial pH is 7.5, which is alkalemic because it is higher than 7.44.

2. Metabolic or respiratory? The primary process in our patient is overwhelmingly metabolic, as his partial pressure of carbon dioxide (Pco₂) is slightly elevated, a direction that would cause acidosis, not alkalosis.

3. The anion gap (the serum sodium concentration minus the sum of the chloride and bicarbonate concentrations) is normal at 8 mmol/L (DRG:HYBRiD-XL Immunoassay and Clinical Chemistry Analyzer, reference range 8–16).

4. Is the disturbance compensated? We have determined that this patient has a metabolic alkalemia; the question now is whether there is any compensation for the primary disturbance.

In metabolic alkalosis, the Pco₂ may increase by approximately 0.6 mm Hg (range 0.5–0.8) above the nominal normal level of 40 mm Hg for each 1-mmol/L increase in bicarbonate above the nominal normal level of 25 mmol/L.⁴ If the patient requires oxygen, the calculation may be unreliable, however, as hypoxemia may have an overriding influence on respiratory drive.

Patients with chronically high Pco₂ levels such as those with chronic obstructive pulmonary disease can become accustomed to high carbon dioxide levels and lose their hyper-
capnic respiratory drive. Giving oxygen supplementation is thought to decrease respiratory drive in these patients, so that they will breathe slower and retain more carbon dioxide. There is some degree of respiratory compensation for metabolic alkalosis that occurs by breathing less, though it is limited overall—even in very alkalotic patients, breathing less results in CO₂ retention, which, by displacing O₂ molecules in the alveoli, will in turn result in hypoxia. The brain then senses the hypoxia and makes one breathe faster, thereby limiting this compensation. 

This patient’s serum bicarbonate level is 40 mmol/L, or 15 mmol/L higher than the nominal normal level. If he is compensating, his Pco₂ should be 40 + (15 × 0.6) = 49 mm Hg, and in fact it is 51 mm Hg, which is within the normal range of expected compensation (47.5–52 mm Hg). Therefore, yes, he is compensating for the primary disturbance.  

5. In metabolic acidosis, is there a delta gap? As our patient has metabolic alkalosis, not acidosis, this question does not apply in this case.

 

 

WHICH TEST TO FIND THE CAUSE?

2. Which is the best test to order next to determine the cause of this patient’s hypokalemic metabolic alkalosis?

• Serum magnesium level
• Spot urine chloride
• Renal ultrasonography
• 24-hour urine collection for sodium, potassium, and chloride

The first step in the algorithm for hypokalemic metabolic alkalosis (Figure 1) is to obtain a spot urine chloride measurement. If this value is low, the hypokalemic metabolic alkalosis is volume-responsive; if it is high, the disturbance is volume-independent.

The patient’s loop diuretic is withheld for 12 hours and a spot urine chloride is obtained, which is reported as 44 mmol/L. This high value suggests that a volume-independent hypo­kalemic metabolic alkalosis is present with potassium depletion.

As for the other answer choices:

Serum magnesium. Though hypomagnesemia can cause hypokalemia due to lack of inhibition of renal outer medullary potassium channels and subsequent increased excretion of potassium in the apical tubular membrane, it is not independently associated with acid-base disturbances.⁵

Renal ultrasonography gives information about structural kidney disease but is of limited utility in identifying the cause of hypokalemic metabolic alkalosis.

A 24-hour urine collection is unnecessary in this setting and would ultimately result in delay in diagnosis, as spot urine chloride is a more efficient means of rapidly distinguishing volume-responsive vs volume-independent causes of hypokalemic metabolic alkalosis.⁶

IS HIS HYPERTENSION SECONDARY? IF SO, WHAT IS THE CAUSE?

Several features of this case suggest that the patient’s hypertension is secondary rather than primary. It is of recent onset. The patient’s family history is noncontributory, and his hypertension is resistant to the use of maximum doses of 3 antihypertensive agents.

3. Which of the following causes of secondary hypertension is not commonly associated with hypokalemia and metabolic alkalosis?

• Hyperaldosteronism
• Liddle syndrome
• Cushing syndrome
• Renal parenchymal disease
• Chronic licorice ingestion

Renal parenchymal disease is a cause of resistant hypertension, but it is not characterized by metabolic alkalosis, hypokalemia, and  elevated urine chloride,⁷ while the others listed here—hyperaldosteronism, Liddle syndrome, Cushing syndrome, and chronic licorice ingestion­—are. Other common causes of resistant hypertension without these metabolic abnormalities include obstructive sleep apnea, alcohol abuse, and nonadherence to treatment.

While treatment of hypertension with loop diuretics can result in hypokalemia and metabolic alkalosis due to the effect of these drugs on potassium reabsorption in the loop of Henle, the patient’s hypokalemia persisted after this agent was withdrawn.⁸

Causes of hypokalemic metabolic alkalosis with and without hypertension are further delineated in Figure 1.

Additional diagnostic testing: Plasma renin and plasma aldosterone

At this juncture, the differential diagnosis for this patient’s potassium depletion, metabolic alkalosis, high urine chloride, and hypertension has been narrowed to primary or secondary hyperaldosteronism, surreptitious mineralocorticoid ingestion, Cushing syndrome, licorice ingestion, Liddle syndrome, or one of the 3 hydroxylase deficiencies (11-, 17-, and 21-) (Figure 1).

Although clues in the history, physical examination, and imaging may suggest a specific cause of his abnormal laboratory values, the next step in the diagnostic workup is to measure the plasma renin and aldosterone levels (Table 3).

 

HYPERALDOSTERONISM

4. Hyperaldosteronism is associated with which of the following patterns of renin and aldosterone values?

• High renin, high aldosterone, normal ratio of plasma aldosterone concentration (PAC) to plasma renin activity (PRA)
• Low renin, low aldosterone, normal PAC–PRA ratio
• Low renin, high aldosterone, high PAC–PRA ratio
• High renin, low aldosterone, low PAC–PRA ratio

The pattern of low renin, high aldosterone, and high PAC–PRA ratio is associated with hyperaldosteronism.

Primary hyperaldosteronism

Primary hyperaldosteronism is one of the most common causes of resistant hypertension and is underappreciated, being diagnosed in up to 20% of patients referred to hypertension specialty clinics.⁷ Potassium levels may be normal, likely contributing to its lack of recognition in this target population.

Primary hyperaldosteronism should be suspected in patients who have a plasma aldosterone PAC–PRA ratio greater than 20 with elevated plasma aldosterone concentrations
(> 15 ng/dL).

Persistently elevated aldosterone levels in the setting of elevated plasma volume is proof that aldosterone secretion is independent of the renin-angiotensin-aldosterone axis, and therefore is autonomous (secondary to adrenal tumor or hyperplasia). Further testing in the form of oral salt loading, saline infusion, or fludrocortisone (a sodium-retaining steroid) administration is thus required to confirm inappropriate, autonomous aldosterone secretion.⁹

After establishing the diagnosis of primary hyperaldosteronism, one should determine the subtype (ie, due to an adrenal carcinoma, unilateral hypersecreting adenoma, or unilateral or bilateral hyperplasia). Further testing includes adrenal computed tomography (CT) to rule out adrenal carcinomas, which are suspected with adenomas larger than 4 cm. Though part of the diagnostic workup, CT as a means of confirmational testing alone does not preclude the possibility of bilateral adrenal hyperplasia in some patients, even in the presence of an adrenal adenoma. For this reason, adrenal venous sampling is required to definitively determine whether the condition is due to a hypersecreting adrenal adenoma or unilateral or bilateral hyperplasia.^9,10

Treatment of primary hyperaldosteronism depends on the subtype of the disease and involves salt restriction in addition to an aldosterone antagonist (spironolactone or eplerenone in the case of bilateral disease) or surgery (unilateral disease).^9,11,12

Secondary hyperaldosteronism

Secondary hyperaldosteronism should be suspected when plasma renin and aldosterone levels are both elevated with a PAC–PRA ratio less than 10.

This pattern is most commonly seen with diuretic use but can also be a consequence of renal artery stenosis or, rarely, a renin-secreting tumor.¹³ Renal artery stenosis is a common finding in patients with hypertension undergoing cardiac catheterization, which is not surprising as more than 90% of such stenoses are atherosclerotic.⁷ Renin-secreting tumors are exceedingly rare, with fewer than 100 cases reported in the literature, and are more common in younger individuals.¹³

Our patient has low-normal aldosterone and plasma renin

On further testing, this patient’s plasma aldosterone level is 2.55 ng/dL (normal < 15 ng/dL), his plasma renin activity is 0.53 ng/mL/hour (normal 0.2–2.8 ng/mL/hour), and his PAC–PRA ratio is therefore 4.81.

The categories discussed thus far have included primary and secondary hyperaldosteronism, which typically do not present with low to normal levels of both renin and aldosterone. Surreptitious mineralocorticoid use could present in this manner, but is unlikely in this patient, whose medications do not include fludrocortisone.

The low-normal values thus lead to consideration of a third category: apparent mineralocorticoid excess. Diseases in this category such as Cushing disease or adrenocorticotropic hormone (ACTH) excess are characterized by increases in corticosteroids so that the potassium depletion, metabolic alkalosis, and hypertension are not a consequence of renin and aldosterone but rather the excess corticosteroids.¹⁴

Causes of apparent mineralocorticoid excess

There are several possible causes of mineralocorticoid excess associated with hypertension and hypokalemic metabolic alkalosis not due to renin and aldosterone.

Chronic licorice ingestion in high volumes is one such cause and is thought to result in inhibition of 11B-hydroxysteroid dehydrogenase or possibly cortisol oxidase by licorice’s active component, glycyrrhetinic acid. This inhibition results in an inability to convert cortisol to cortisone. The cortisol excess binds to mineralocorticoid receptors, and acting like aldosterone, results in hypertension and hypokalemic metabolic alkalosis as well as feedback inhibition of renin and aldosterone levels.¹⁵

Partial hydroxylase deficiencies, though rare, should also be considered as a cause of hypokalemic metabolic alkalosis, hypertension, and, potentially, hirsutism and clitoromegaly in women. They can be diagnosed with elevated levels of 17-ketosteroids and dehydroepiandrosterone sulfate, both of which, in excess, may act on aldosterone receptors in a manner similar to cortisol.¹⁶

Liddle syndrome, a rare autosomal dominant condition, may also present with suppressed levels of both renin and aldosterone. In contrast to the disorders of nonaldosterone mineralocorticoid excess, however, the sodium channel defect in Liddle syndrome is characterized by a primary increase in sodium reabsorption in the collecting tubule and potassium wasting. The resultant volume expansion leads to suppressed renin and aldosterone levels and hypertension with low potassium and elevated bicarbonate concentrations.¹⁷

Liddle syndrome is commonly diagnosed in childhood but may go unrecognized due to occasional absence of hypokalemia at presentation. Potassium-sparing diuretics such as amiloride or triamterene are the mainstays of treatment.¹⁸

Hypercortisolism results in hypokalemic metabolic alkalosis through the effect of excess cortisol on mineralocorticoid receptors, similar to what occurs in chronic licorice ingestion. Under normal conditions, 11B-hydroxysteroid dehydrogenase converts cortisol to cortisone and is the rate-limiting step in the mineralocorticoid action of cortisol. When plasma cortisol levels are in excess, however, the enzyme is saturated so that its action is insufficient, resulting in cortisol binding to mineralocorticoid receptors to produce effects similar to that of aldosterone on acid-base and electrolyte balance and blood pressure.¹⁹

The increase in blood pressure that is associated with elevated plasma levels of cortisol is not attributable solely to its effect on mineralocorticoid receptors, however. The pathogenesis is multifactorial and not fully understood, but it also is thought to involve increased peripheral vascular sensitivity to adrenergic agonists, increased hepatic production of angiotensinogen, as well as direct and indirect cardiotoxic effects via metabolic and electrolyte aberrations.²⁰ Other common effects and manifestations of hypercortisolism are listed in Table 4.

Rates of cardiovascular and all-cause mortality are increased in patients with long-term hypercortisolism, even after plasma concentrations of cortisol are normalized.²¹

Figure 2 shows the cascade of the hypothalamic-pituitary-adrenal axis.

 

 

TESTING FOR HYPERCORTISOLISM IN OUR PATIENT

Given the patient’s clinical presentation and laboratory and imaging findings with normal plasma renin and aldosterone levels, a workup for suspected hypercortisolism is initiated.

Initial diagnostic testing for hypercortisolism depends on the degree of clinical suspicion. In those with low probability of the disease, testing should consist of 1 of the following, as a single negative test may be sufficient to rule out the disease:

• 24-hour urinary cortisol levels
• Overnight dexamethasone suppression testing
• Late-night salivary cortisol measurements.

In those with a high index of suspicion, 2 of the aforementioned tests should be performed, as 1 normal result may not be sufficient to exclude the diagnosis.^22,23

A 24-hour urinary cortisol collection and overnight dexamethasone suppression test are obtained. His 24-hour urinary free cortisol level is elevated at 6,600 µg (normal 4–100), and suppression testing with 8 mg of dexamethasone (a form of “high-dose” testing)demonstrates only an 8% decline in serum cortisol levels. Cortisol should generally drop more than 90%.

Morning serum cortisol concentration is less than 5 µg/dL (140 nmol/L) in most patients with Cushing disease (ie, a pituitary tumor), and is usually undetectable in normal subjects. Only about 50% of neuroendocrine ACTH-secreting tumors will suppress with this test.

The patient’s clinical presentation, in conjunction with his diagnostic testing, are thus consistent with Cushing syndrome.

CUSHING SYNDROME

Cushing syndrome is most often exogenous or iatrogenic, ie, a result of supraphysiologic doses of glucocorticoids used to treat a variety of inflammatory, autoimmune, and neoplastic conditions.

Endogenous Cushing syndrome, on the other hand, is rare, with an estimated prevalence of 0.7 to 2.4 cases per million per year. ACTH-dependent causes account for 80% of endogenous Cushing syndrome cases, with ACTH-secreting pituitary adenomas (Cushing disease) accounting for 75% to 80% and ectopic ACTH secretion accounting for 15% to 20%. Less than 1% of cases are due to tumors that produce corticotropin-releasing hormone (CRH).

ACTH-independent Cushing syndrome is diagnosed in 20% of endogenous cases and is most commonly caused by a unilateral adrenal tumor. Rare causes of ACTH-independent disease include adrenal carcinoma, McCune-Albright syndrome, and adrenal hyperplasia.²⁴

The patient’s ACTH is high

To determine whether this is an ACTH-dependent or independent process, the next step is to order an ACTH level. His ACTH level is high at 107 pg/mL (normal < 46 pg/mL), confirming the diagnosis of ACTH-dependent Cushing syndrome.

To find out if this ACTH-dependent process is due to a pituitary adenoma, magnetic resonance imaging (MRI) of the pituitary is obtained but is normal.

Large masses (> 6 mm) strongly suggest Cushing disease, but these tumors are often small and may be missed even with more advanced imaging techniques. Corticotropin-secreting adenomas arising from normal cells in the pituitary retain some sensitivity to glucocorticoid negative feedback and CRH stimulation, and thus high-dose dexamethasone suppression testing in conjunction with CRH stimulation testing can be used to differentiate Cushing disease from ectopic ACTH secretion.^24,25 Both of these tests have poor diagnostic accuracy, however, and thus inferior petrosal sampling remains the gold standard for the diagnosis of Cushing disease.

Given this patient’s history of smoking and a right hilar pulmonary opacity on chest radiography, inferior petrosal sampling was deferred in favor of CT of the chest, which showed a right consolidative lung lesion (Figure 3). Subsequent CT-guided fine-needle biopsy demonstrated a small-cell carcinoma.

ACTH-SECRETING TUMORS

5. Cushing syndrome due to ectopic ACTH secretion is most commonly attributed to which of the following tumors?

• Small-cell lung carcinoma
• Pancreatic carcinoma
• Medullary thyroid carcinoma
• Gastrinoma

Severe cases of Cushing syndrome are often attributable to ectopic ACTH secretion due to an underlying malignancy, most commonly small-cell lung carcinoma or neuroendocrine tumors of pulmonary origin. Other causes include pancreatic and thymic neuroendocrine tumors, gastrinomas, and medullary thyroid carcinoma.^25,26

Because most ACTH-producing tumors are intrathoracic, initial imaging in cases of suspected ectopic ACTH secretion should focus on the chest, with CT the usual first choice. Octreotide scintigraphy can also be useful in localizing disease, as many neuroendocrine tumors express somatostatin receptors. Specialized positron-emission tomography scans may also be helpful in tumor identification.²⁴

 

 

TREATMENT OF CUSHING SYNDROME DUE TO ECTOPIC ACTH SECRETION

6. Which of the following is most appropriate medical therapy for suppression of cortisol secretion in Cushing syndrome due to ectopic ACTH secretion?

• Spironolactone
• Dexamethasone
• Somatostatin
• Estrogen
• Ketoconazole

Hyperglycemia, hypokalemia, hypertension, psychiatric disturbances, venous thromboembolism, and systemic infections appear to be common in ectopic ACTH syndrome and often correlate with the degree of hypercortisolemia. Severe Cushing syndrome due to ectopic ACTH secretion is an emergency requiring prompt control of cortisol secretion.

First-line treatments include steroidogenesis inhibitors (ketoconazole, metyrapone, etomidate, mitotane) and glucocorticoid receptor antagonists (mifepristone). High-dose spironolactone and eplerenone can also be used to treat the hypertension and hypokalemia associated with mineralocorticoid receptor stimulation. Definitive treatment involves surgical resection, chemotherapy, or radiotherapy when applicable.^24,25

After confirmation of the diagnosis, the patient is prescribed ketoconazole and spironolactone, with substantial improvement. He subsequently is started on combination chemotherapy and radiation therapy for his small-cell lung carcinoma.

DISCUSSION

The differential diagnosis for hypokalemia is broad and relies on information obtained during the history and physical examination, followed by interpretation of selected laboratory results. Myriad pathologies in diverse organ systems, eg, diarrhea, renal tubular acidosis, and adrenal disease, may be responsible for a low serum potassium. Further categorizing potassium depletion on the basis of an associated acid-base disturbance, such as metabolic alkalosis, allows one to use an algorithmic approach that can identify specific etiologies responsible for both the potassium and the acid-base disturbances.

Using the spot urine chloride in the setting of hypokalemic metabolic alkalosis with or without hypertension can narrow the differential diagnosis and allow additional clinical findings to guide clinical problem-solving and decision-making, even for conditions not commonly encountered in routine medical practice.

Obtaining renin and aldosterone measurements in patients with potassium depletion, metabolic alkalosis, high urine chloride excretion, and hypertension permits further categorization into 3 clinical groups: elevated aldosterone and renin (secondary hyperaldosteronism), elevated aldosterone and low renin (primary hyperaldosteronism), or apparent mineralocorticoid excess wherein neither renin nor aldosterone are responsible for the syndrome.

The patient in our case had apparent mineralocorticoid excess as a consequence of an ACTH-producing small-cell carcinoma.