Plasma amyloid-β oligomers level is a biomarker for Alzheimer's disease diagnosis

Amyloid beta (A beta), especially A beta oligomers, is important in Alzheimer's disease (AD) pathogenesis. We studied plasma A beta(40), A beta(42), and A beta oligomers levels in 44 AD patients and 22 non-demented controls. Cognitive functions were assessed by Chinese version of mini-mental state examination (MMSE), Abbreviated Metal Test (AMT), Alzheimer's Disease Assessment Scale Cognitive Subscale (ADAS-cog). Plasma A beta monomers and oligomers levels were measured by ELISA. We found that the median plasma A beta(40) and A beta(42) levels were similar between AD and controls, and without significant correlation with cognition. Plasma A beta oligomers level was higher in AD than controls (642.54 ng/ml [range 103.33-2676.93] versus 444.18 ng/ml [range 150.19-1311.18], p = 0.047), and negatively correlated with cognition. In multivariate logistic regression analysis, the highest tertile of A beta oligomers levels showed an increased risk of AD than the combined group of middle and lowest tertiles (OR = 8.85, p = 0.013), after adjustment of gender, age and APOE4 genotype. Increased plasma A beta oligomers level was associated with decreased MMSE and AMT scores (p = 0.037, p = 0.043, respectively) and increased ADAS-cog score (p = 0.036), suggesting negative correlation with cognitive function. We concluded that plasma A beta oligomers level is an useful biomarker for AD diagnosis. (C) 2012 Elsevier Inc. All rights reserved.