Fully automated chemiluminescence enzyme immunoassays showing high correlation with immunoprecipitation mass spectrometry assays for -amyloid (1-40) and (1-42) in plasma samples

Blood based beta-amyloid (A beta) assays that can predict amyloid positivity in the brain are in high demand. Current studies that utilize immunoprecipitation mass spectrometry assay (IP-MS), which has high specificity for measuring analytes, have revealed that precise plasma A beta assays have the potential to detect amyloid positivity in the brain. In this study, we developed plasma A beta 40 and A beta 42 immunoassays using a fully automated immunoassay platform that is used in routine clinical practice. Our assays showed high sensitivity (limit of quantification: 2.46 pg/mL [A beta 40] and 0.16 pg/mL [A beta 42]) and high reproducibility within-run (coefficients of variation [CVs]: <3.7% [A beta 40]and <2.0% [A beta 42]) and within laboratory (CVs: <4.6% [A beta 40] and <5.3% [A beta 42]). The interference from plasma components was less than 10%, and the cross-reactivity with various lengths of A beta peptides was less than 0.5%. In addition, we found a significant correlation between the IP-MS method and our immunoassay (correlation coefficients of Pearson's r: 0.91 [A beta 40] and 0.82 [A beta 42]). Our new method to quantify plasma A beta 40 and A beta 42 provides clinicians and patients with a way to continuously monitor disease progression. (c) 2021 The Authors. Published by Elsevier Inc.