Independent information from cerebrospinal fluid amyloid-b and florbetapir imaging in

Reduced cerebrospinal fluid amyloid-b42 and increased retention of florbetapir positron emission tomography are biomarkers reflecting cortical amyloid load in Alzheimer’s disease. However, these measurements do not always agree and may represent partly different aspects of the underlying Alzheimer’s disease pathology. The goal of this study was therefore to test if cerebrospinal fluid and positron emission tomography amyloid-b biomarkers are independently related to other Alzheimer’s disease markers, and to examine individuals who are discordantly classified by these two biomarker modalities. Cerebrospinal fluid and positron emission tomography amyloid-b were measured at baseline in 769 persons [161 healthy controls, 68 subjective memory com-plaints, 419 mild cognitive impairment and 121 Alzheimer’s disease dementia, mean age 72 years (standard deviation 7 years), 47 % females] and used to predict diagnosis, APOE e4 carriage status, cerebral blood flow, cerebrospinal fluid total-tau and phosphorylated-tau levels (cross-sectionally); and hippocampal volume, fluorodeoxyglucose positron emission tomography results and Alzheimer’s Disease Assessment Scale-cognitive subscale scores (longitudinally). Cerebrospinal fluid and positron emission tomography amyloid-b were highly correlated, but adjusting one of these predictors for the other revealed that they both provided partially independent information when predicting diagnosis, APOE e4, hippocampal volume, metabolism, cognition, total-tau and phosphorylated-tau (the 95 % confidence intervals of the adjusted effects did not include zero). Cerebrospinal fluid amyloid-b was more strongly related to APOE e4 whereas positron emission tomography amyloid-b was more strongly related to tau levels (P50.05). Discordance (mainly isolated cerebrospinal fluid amyloid-b positivity) differed by diagnostic group (P5 0.001) and wa