Effect of apolipoprotein E phenotype on the association of plasma amyloid β and amyloid positron emission tomography imaging in Japan

INTRODUCTION The plasma concentration of beta-amyloid (Aβ) has been considered another biomarker of Alzheimer's disease and was reportedly associated with cortical Aβ accumulation. METHODS We analyzed 28 subjects with apolipoprotein E4 (ApoE4; E4 group) and 89 subjects without ApoE4 (non-E4 group) to determine the association between cortical Aβ accumulation by standard uptake value ratio with [18F]florbetapir positron emission tomography and plasma Aβ1-40 and Aβ1-42. RESULTS Aβ1-42/Aβ1-40 correlated significantly with mean regional [18F]florbetapir standard uptake value ratio in the non-E4 group (R2 = 0.06, P = .02) but not in the E4 group, and receiver operating characteristic curve analysis for Aβ1-42/Aβ1-40 in the non-E4 group showed sensitivity (92.9%) and specificity (45.9%) with a cutoff value of 0.150 for Aβ positivity. DISCUSSION We verified that the correlation between Aβ1-42/Aβ1-40 and Aβ accumulation differed according to ApoE phenotype. The high sensitivity of plasma Aβ1-42/Aβ1-40 for Aβ positivity in non-E4 subjects indicated a possible role of plasma Aβ1-42/Aβ1-40 as a screening biomarker before amyloid positron emission tomography in clinical settings.