PET Detection of Amyloid Levels Equal to Immunohistochemistry

Amyloid levels detected by florbetapir-PET standard uptake value ratio characterizes AD, MCI

13 july 2011-- Detection of amyloid levels by positron emission tomography (PET), measuring fluorine 18-labeled flutemetamol (florbetapir) uptake by the brain cortex, is in concordance with immunohistochemical estimation; and the florbetapir-PET standard uptake value ratios (SUVRs) help characterize amyloid levels in patients with Alzheimer's disease (AD) and mild cognitive impairment (MCI), according to two studies published online July 11 in the Archives of Neurology.

David A. Wolk, M.D., from the University of Pennsylvania in Philadelphia, and colleagues investigated the concordance of in vivo quantitative estimates of florbetapir brain uptake in PET scans with immunohistochemical estimates of amyloid levels in seven patients who had a previous cortical biopsy. They found a complete agreement between florbetapir-PET scans and histology. Taking time from biopsy as a covariate, they identified a significant relationship between florbetapir uptake and percentage of area of amyloid measured by a monoclonal antibody raised against amyloid.

Adam S. Fleisher, M.D., from the Banner Alzheimer's Institute in Phoenix, and colleagues characterized florbetapir-PET measurements of fibrillar β-amyloid (Aβ) burden and compared mean cortical florbetapir SUVRs in 68 patients with AD, 60 with MCI, and 82 older healthy controls (OHCs). Participants with probable AD and MCI, and OHCs differed significantly in mean cortical florbetapir SUVRs, in the percentage meeting SUVR criteria of levels of amyloid associated with AD (80.9, 40.0, and 20.7 percent, respectively), and in percentage meeting SUVR criteria for the presence of any identifiable Aβ (85.3, 46.6, and 28.1 percent, respectively).

"The findings of our analysis confirm the ability of florbetapir-PET SUVRs to characterize amyloid levels in clinically probable AD, MCI, and OHC groups using continuous and binary measures of fibrillar Aβ burden," the authors write.

Several authors from Wolk's study disclosed financial relationships with GE Healthcare, which also funded the study. Several authors from Fleisher's study disclosed financial ties to the pharmaceutical industry, including Avid Radiopharmaceuticals, a wholly owned subsidiary of Eli Lilly, which funded the study.

Abstract - Wolk
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