Preanalytical stability of plasma biomarkers for Alzheimer's disease pathology

Abstract

Introduction Plasma tests have demonstrated high diagnostic accuracy for identifying Alzheimer's disease pathology. To facilitate the transition to clinical utility, we assessed whether plasma storage duration and temperature affect the biomarker concentrations. Methods Plasma samples from 13 participants were stored at +4°C and +18°C. Concentrations of six biomarkers were measured after 2, 4, 6, 8, 10, and 24 h by single molecule array assays. Results Phosphorylated tau 181 (p-tau181), phosphorylated tau 231 (p-tau231), neurofilament light (NfL), and glial fibrillary acidic protein (GFAP) concentrations were unchanged both when stored at +4°C and +18°C. Amyloid-β 40 (Aβ40) and amyloid-β 42 (Aβ42) concentrations were stable for 24 h at +4°C but declined when stored at +18°C for longer than 6 h. This decline did not affect the Aβ42/Aβ40 ratio. Discussion Plasma samples can be stored for 24 h at +4°C or +18°C and result in valid assay results for p-tau181, p-tau231, Aβ42/Aβ40 ratio, GFAP, and NfL. HIGHLIGHTS Plasma samples were stored for 24 h at +4°C and +18°C, mimicking clinical practice. Concentrations for Alzheimer's disease biomarkers were measured at six time-points. p-tau181, p-tau231, NfL, and GFAP concentrations were unchanged during the experiment. Storage at +18°C affected Aβ40 and Aβ42 concentrations while storage at +4°C did not. The Aβ42/Aβ40 ratio was unaffected. These plasma tests seem suitable for use in general practice.