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

Background: Plasma beta-amyloid (A beta) 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 A beta is one of the major hallmarks of AD pathogenesis in the brain. However, the association between plasma A beta levels and AD diagnosis is still unclear due to the instability and inaccurate measurements of plasma A beta levels in the blood of patients with AD. If a consistent value of plasma A beta from the blood can be obtained, this might help determine whether plasma A beta is a potential biomarker for AD diagnosis. Methods: We predicted the brain amyloid deposit by measuring the plasma A beta 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 A beta 42 and A beta 40 ( MPP-A beta 42 and MPP-A beta 40) in a stable manner using xMAP technology. Results: MPP-A beta 40 and MPP-A beta 42/40 (MPP-A beta s) were significantly different between subjects with positive amyloid deposition (PiB+) and those with negative amyloid deposition (PiB-) (P < 0.0001). Furthermore, MPP-A beta 40 (P < 0.0001, r = 0.23) and MPP-A beta 42/40 ratio (P < 0.0001, r = -0.23) showed significant correlation with global PiB deposition (standardized uptake value ratio). In addition, our integrated multivariable (MPP-A beta 42/40, gender, age, and apolipoprotein E genotypes) logistic regression model proposes a new standard for the prediction of cerebral amyloid deposition. Conclusions: MPP-A beta might be one of the potential blood biomarkers for the prediction of PiB-PET positivity in the brain.