Cognition and amyloid load in Alzheimer disease imaged with florbetapir F 18 (AV-45) positron emission tomography

Objective: To examine the association between regional brain uptake of a novel amyloid positron emission tomography (PET) tracer florbetapir F 18 ([ ¹⁸F]-AV-45) and cognitive performance in a pilot study. Design: Cross-sectional comparison of [¹⁸F]-AV- 45 in AD patients versus controls. Setting: Three specialty memory clinics. Participants: Eleven participants with probable Alzheimer disease (AD) by NINDS/ADRDA criteria and 15 healthy comparison (HC) participants. Measurements: Participants underwent PET imaging following a 370 MBq (10 mCi) intravenous administration of [ ¹⁸F]-AV-45. Regional/cerebellar standardized uptake value ratios (SUVRs) were calculated. Cognition was assessed using Mini-Mental State Examination, Alzheimer's Disease Assessment Scale-Cognitive subscale (ADAS-Cog), Wechsler Logical Memory IA (immediate recall) test (LMIA), and verbal category fluency. Results: Greater [¹⁸F]-AV-45 SUVR was associated with poorer performance on all cognitive tests. In the HC group, occipital, parietal, precuneus, temporal, and cortical average SUVR was associated with greater ADAS-Cog, and greater anterior cingulate SUVR was associated with lower LMIA. Two HC participants had [¹⁸F]-AV-45 cortical/cerebellar SUVR greater than 1.5, one of whom had deficits in episodic recall and on follow-up met criteria for amnestic mild cognitive impairment. Conclusion: [ ¹⁸F]-AV-45 SUVR in several brain regions was associated with worse global cognitive performance particularly in HC, suggesting its potential as a marker of preclinical AD.