Preanalytical stability of plasma biomarkers for Alzheimer's disease pathology.

Abstract

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. 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 24h by single molecule array assays. 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 24h at +4°C but declined when stored at +18°C for longer than 6h. This decline did not affect the Aβ42/Aβ40 ratio. Plasma samples can be stored for 24h at +4°C or +18°C and result in valid assay results for p-tau181, p-tau231, Aβ42/Aβ40 ratio, GFAP, and NfL. Plasma samples were stored for 24h 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.