Chemically treated plasma Aß is a potential blood-based biomarker for screening cerebral amyloid deposition.

ABSTRACT

BACKGROUND: Plasma ß-amyloid (Aß) is a potential candidate for an Alzheimer's disease (AD) biomarker because blood is an easily accessible bio-fluid, which can be collected routinely, and Aß is one of the major hallmarks of AD pathogenesis in the brain. However, the association between plasma Aß levels and AD diagnosis is still unclear due to the instability and inaccurate measurements of plasma Aß levels in the blood of patients with AD. If a consistent value of plasma Aß from the blood can be obtained, this might help determine whether plasma Aß is a potential biomarker for AD diagnosis. METHODS: We predicted the brain amyloid deposit by measuring the plasma Aß levels. This cross-sectional study included 353 participants (215 cognitively normal, 79 with mild cognitive impairment, and 59 with AD dementia) who underwent Pittsburgh-compound B positron emission tomography (PiB-PET) scans. We treated a mixture of protease inhibitors and phosphatase inhibitors (MPP) and detected plasma Aß42 and Aß40 (MPP-Aß42 and MPP-Aß40) in a stable manner using xMAP technology. RESULTS: MPP-Aß40 and MPP-Aß42/40 (MPP-Aßs) were significantly different between subjects with positive amyloid deposition (PiB+) and those with negative amyloid deposition (PiB-) (P < 0.0001). Furthermore, MPP-Aß40 (P < 0.0001, r = 0.23) and MPP-Aß42/40 ratio (P < 0.0001, r = -0.23) showed significant correlation with global PiB deposition (standardized uptake value ratio). In addition, our integrated multivariable (MPP-Aß42/40, gender, age, and apolipoprotein E genotypes) logistic regression model proposes a new standard for the prediction of cerebral amyloid deposition. CONCLUSIONS: MPP-Aß might be one of the potential blood biomarkers for the prediction of PiB-PET positivity in the brain.