Plasma apolipoprotein E and Alzheimer disease risk: the AIBL study of aging.

There is mounting evidence for the contribution of apoE to the pathophysiology of Alzheimer disease (AD). Studies also indicate that plasma apoE levels may reflect disease status, suggesting that apoE is a potential AD biomarker. However, while some studies of apoE levels in plasma have presented correlations with AD pathology, others have not. Thus, there is a lack of consensus as to the suitability of plasma apoE as an AD biomarker. The major objective of this cross-sectional study was to investigate total plasma apoE as well as levels of the apoE4 form in a large, highly characterized cohort which included both healthy controls and participants with early-stage AD.