Preanalytical stability of plasma biomarkers for Alzheimer's disease pathology

IntroductionPlasma 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. MethodsPlasma samples from 13 participants were stored at +4 degrees C and +18 degrees C. Concentrations of six biomarkers were measured after 2, 4, 6, 8, 10, and 24 h by single molecule array assays. ResultsPhosphorylated 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 degrees C and +18 degrees C. Amyloid-beta 40 (A beta 40) and amyloid-beta 42 (A beta 42) concentrations were stable for 24 h at +4 degrees C but declined when stored at +18 degrees C for longer than 6 h. This decline did not affect the A beta 42/A beta 40 ratio. DiscussionPlasma samples can be stored for 24 h at +4 degrees C or +18 degrees C and result in valid assay results for p-tau181, p-tau231, A beta 42/A beta 40 ratio, GFAP, and NfL. HIGHLIGHTSPlasma samples were stored for 24 h at +4 degrees C and +18 degrees 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 degrees C affected A beta 40 and A beta 42 concentrations while storage at +4 degrees C did not. The A beta 42/A beta 40 ratio was unaffected.These plasma tests seem suitable for use in general practice.

Automated summary

This study found that plasma storage duration and temperature do not affect the concentrations of Alzheimer's disease biomarkers. The plasma samples can be stored at +4 degrees C or +18 degrees C for 24 hours without impacting the assay results for p-tau181, p-tau231, A beta 42/A beta 40 ratio, GFAP, and NfL.