Do Clinical Characteristics Correlate With Florbetapir-PET Scan Results?

PHILADELPHIA—Clinical characteristics alone cannot distinguish between patients with positive florbetapir F18 PET scans and patients with negative scans, according to research presented at the 66th Annual Meeting of the American Academy of Neurology.

Florbetapir highly correlates with the presence and density of β-amyloid neuritic plaques on autopsy. Thus, the research indicates that neurologists cannot yet use clinical characteristics to identify patients at risk of receiving a misdiagnosis of Alzheimer’s disease.

“Results of amyloid PET can aid in the accurate diagnosis of dementia attributable to Alzheimer’s disease, though other biomarker tests, many not yet developed, would be needed to determine the underlying disease in those with negative florbetapir F18 PET scans,” said Elisabeth K. Degenhardt, Senior Clinical Research Scientist at Lilly USA in Indianapolis.

An Analysis of 390 Patients With Dementia
Ms. Degenhardt and her colleagues examined data for 390 patients age 55 or older with Alzheimer’s disease. All participants met criteria from the National Institute of Neurological and Communicative Disorders and Stroke and the Alzheimer’s Disease and Related Disorders Association for probable Alzheimer’s disease. Eligible participants were enrolled in one of two phase III registration trials of solanezumab and had a florbetapir PET scan at a prerandomization visit.

The researchers derived a standardized uptake value ratio (SUVR) across a composite of six cortical regions of interest, compared with the whole cerebellum. The regions of interest included frontal, temporal, parietal, precuneus, anterior cingulate, and posterior cingulate regions. Patients with a composite cortical SUVR of 1.1 or greater were considered to have a positive scan.

Of the 390 patients, 216 were female. Patients’ mean age was approximately 74. Mean disease duration was about four years.

More Than One-Fifth of Patients Had Negative Scans
Florbetapir PET scans were negative in 22.4% of patients. Of patients with mild dementia, 27.5% had negative scans. Of patients with moderate dementia, 13.1% had negative scans.

Participants with negative florbetapir PET scans had less cognitive impairment on the Alzheimer’s Disease Assessment Scale–Cognitive Subscale and the Mini-Mental State Examination than patients with positive scans. However, patients with negative scans had significantly worse function in activities of daily living than did patients with positive scans.

Approximately 23% of patients with negative florbetapir PET scans carried the APOE e4 allele, compared with 63% of patients with positive florbetapir PET scans. In addition, the researchers found a significant relationship between sex and amyloid status. Negative scans occurred in 17.6% of female patients, compared with 28.2% of male patients.

The investigators found no differences between patients with positive scans and those with negative scans in terms of age, education, most functional measures, neuropsychiatric symptoms, and depression. “Our findings are consistent with other studies reporting similar findings in patients clinically diagnosed with Alzheimer’s disease dementia,” concluded Ms. Degenhardt.

—Erik Greb

PHILADELPHIA—Clinical characteristics alone cannot distinguish between patients with positive florbetapir F18 PET scans and patients with negative scans, according to research presented at the 66th Annual Meeting of the American Academy of Neurology.

Florbetapir highly correlates with the presence and density of β-amyloid neuritic plaques on autopsy. Thus, the research indicates that neurologists cannot yet use clinical characteristics to identify patients at risk of receiving a misdiagnosis of Alzheimer’s disease.

“Results of amyloid PET can aid in the accurate diagnosis of dementia attributable to Alzheimer’s disease, though other biomarker tests, many not yet developed, would be needed to determine the underlying disease in those with negative florbetapir F18 PET scans,” said Elisabeth K. Degenhardt, Senior Clinical Research Scientist at Lilly USA in Indianapolis.

An Analysis of 390 Patients With Dementia
Ms. Degenhardt and her colleagues examined data for 390 patients age 55 or older with Alzheimer’s disease. All participants met criteria from the National Institute of Neurological and Communicative Disorders and Stroke and the Alzheimer’s Disease and Related Disorders Association for probable Alzheimer’s disease. Eligible participants were enrolled in one of two phase III registration trials of solanezumab and had a florbetapir PET scan at a prerandomization visit.

The researchers derived a standardized uptake value ratio (SUVR) across a composite of six cortical regions of interest, compared with the whole cerebellum. The regions of interest included frontal, temporal, parietal, precuneus, anterior cingulate, and posterior cingulate regions. Patients with a composite cortical SUVR of 1.1 or greater were considered to have a positive scan.

Of the 390 patients, 216 were female. Patients’ mean age was approximately 74. Mean disease duration was about four years.

More Than One-Fifth of Patients Had Negative Scans
Florbetapir PET scans were negative in 22.4% of patients. Of patients with mild dementia, 27.5% had negative scans. Of patients with moderate dementia, 13.1% had negative scans.

Participants with negative florbetapir PET scans had less cognitive impairment on the Alzheimer’s Disease Assessment Scale–Cognitive Subscale and the Mini-Mental State Examination than patients with positive scans. However, patients with negative scans had significantly worse function in activities of daily living than did patients with positive scans.

Approximately 23% of patients with negative florbetapir PET scans carried the APOE e4 allele, compared with 63% of patients with positive florbetapir PET scans. In addition, the researchers found a significant relationship between sex and amyloid status. Negative scans occurred in 17.6% of female patients, compared with 28.2% of male patients.

The investigators found no differences between patients with positive scans and those with negative scans in terms of age, education, most functional measures, neuropsychiatric symptoms, and depression. “Our findings are consistent with other studies reporting similar findings in patients clinically diagnosed with Alzheimer’s disease dementia,” concluded Ms. Degenhardt.

—Erik Greb

PHILADELPHIA—Clinical characteristics alone cannot distinguish between patients with positive florbetapir F18 PET scans and patients with negative scans, according to research presented at the 66th Annual Meeting of the American Academy of Neurology.

Florbetapir highly correlates with the presence and density of β-amyloid neuritic plaques on autopsy. Thus, the research indicates that neurologists cannot yet use clinical characteristics to identify patients at risk of receiving a misdiagnosis of Alzheimer’s disease.

“Results of amyloid PET can aid in the accurate diagnosis of dementia attributable to Alzheimer’s disease, though other biomarker tests, many not yet developed, would be needed to determine the underlying disease in those with negative florbetapir F18 PET scans,” said Elisabeth K. Degenhardt, Senior Clinical Research Scientist at Lilly USA in Indianapolis.

An Analysis of 390 Patients With Dementia
Ms. Degenhardt and her colleagues examined data for 390 patients age 55 or older with Alzheimer’s disease. All participants met criteria from the National Institute of Neurological and Communicative Disorders and Stroke and the Alzheimer’s Disease and Related Disorders Association for probable Alzheimer’s disease. Eligible participants were enrolled in one of two phase III registration trials of solanezumab and had a florbetapir PET scan at a prerandomization visit.

The researchers derived a standardized uptake value ratio (SUVR) across a composite of six cortical regions of interest, compared with the whole cerebellum. The regions of interest included frontal, temporal, parietal, precuneus, anterior cingulate, and posterior cingulate regions. Patients with a composite cortical SUVR of 1.1 or greater were considered to have a positive scan.

Of the 390 patients, 216 were female. Patients’ mean age was approximately 74. Mean disease duration was about four years.

More Than One-Fifth of Patients Had Negative Scans
Florbetapir PET scans were negative in 22.4% of patients. Of patients with mild dementia, 27.5% had negative scans. Of patients with moderate dementia, 13.1% had negative scans.

Participants with negative florbetapir PET scans had less cognitive impairment on the Alzheimer’s Disease Assessment Scale–Cognitive Subscale and the Mini-Mental State Examination than patients with positive scans. However, patients with negative scans had significantly worse function in activities of daily living than did patients with positive scans.

Approximately 23% of patients with negative florbetapir PET scans carried the APOE e4 allele, compared with 63% of patients with positive florbetapir PET scans. In addition, the researchers found a significant relationship between sex and amyloid status. Negative scans occurred in 17.6% of female patients, compared with 28.2% of male patients.

The investigators found no differences between patients with positive scans and those with negative scans in terms of age, education, most functional measures, neuropsychiatric symptoms, and depression. “Our findings are consistent with other studies reporting similar findings in patients clinically diagnosed with Alzheimer’s disease dementia,” concluded Ms. Degenhardt.

—Erik Greb