Journal Article

A blood-based diagnostic test incorporating plasma Abeta42/40 ratio, ApoE proteotype, and age accurately identifies brain amyloid status: findings from a multi cohort validity analysis

Knapik, Stephanie S, Holubasch, Mary S, Fogelman, Ilana, Braunstein, Joel B, West, Tim, Hu, Yan, Jackson, Erin N, Harpstrite, Scott E, Bateman, Randall J, Yarasheski, Kevin E, Meyer, Matthew R, Verghese, Philip B, Kirmess, Kristopher M, Contois, John H, Holtzman, David M

2021

Overview

The development of blood-based biomarker tests that are accurate and robust for Alzheimer's disease (AD) pathology have the potential to aid clinical diagnosis and facilitate enrollment in AD drug trials. We developed a high-resolution mass spectrometry (MS)-based test that quantifies plasma A[beta]42 and A[beta]40 concentrations and identifies the ApoE proteotype. We evaluated robustness, clinical performance, and commercial viability of this MS biomarker assay for distinguishing brain amyloid status. We used the novel MS assay to analyze 414 plasma samples that were collected, processed, and stored using site-specific protocols, from six independent US cohorts. We used receiver operating characteristic curve (ROC) analyses to assess assay performance and accuracy for predicting amyloid status (positive, negative, and standard uptake value ratio; SUVR). After plasma analysis, sites shared brain amyloid status, defined using diverse, site-specific methods and cutoff values; amyloid PET imaging using various tracers or CSF A[beta]42/40 ratio. Plasma A[beta]42/40 ratio was significantly (p < 0.001) lower in the amyloid positive vs. negative participants in each cohort. The area under the ROC curve (AUC-ROC) was 0.81 (95% CI = 0.77-0.85) and the percent agreement between plasma A[beta]42/40 and amyloid positivity was 75% at the optimal (Youden index) cutoff value. The AUC-ROC (0.86; 95% CI = 0.82-0.90) and accuracy (81%) for the plasma A[beta]42/40 ratio improved after controlling for cohort heterogeneity. The AUC-ROC (0.90; 95% CI = 0.87-0.93) and accuracy (86%) improved further when A[beta]42/40, ApoE4 copy number and participant age were included in the model. This mass spectrometry-based plasma biomarker test: has strong diagnostic performance; can accurately distinguish brain amyloid positive from amyloid negative individuals; may aid in the diagnostic evaluation process for Alzheimer's disease; and may enhance the efficiency of enrolling participants into Alzheimer's disease drug trials.

• Publisher: BioMed Central Ltd
• Subject: Advertising executives / Alzheimer's disease / Apolipoproteins / Brain research / Diagnosis / Mass spectrometry / Medical tests / Scientific equipment and supplies industry