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 [(18)F]florbetapir positron emission tomography and plasma Aβ(1–40) and Aβ(1–42). RESULTS: Aβ(1–42)/Aβ(1–40) correlated significantly with mean regional [(18)F]florbetapir standard uptake value ratio in the non-E4 group (R(2) = 0.06, P = .02) but not in the E4 group, and receiver operating characteristic curve analysis for Aβ(1–42)/Aβ(1–40) 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 Aβ(1–42)/Aβ(1–40) and Aβ accumulation differed according to ApoE phenotype. The high sensitivity of plasma Aβ(1–42)/Aβ(1–40) for Aβ positivity in non-E4 subjects indicated a possible role of plasma Aβ(1–42)/Aβ(1–40) as a screening biomarker before amyloid positron emission tomography in clinical settings.