Evidence-based standardized sample handling protocol for accurate blood-based Alzheimer's disease biomarker measurement: Results and consensus of the Global Biomarker Standardization Consortium

Abstract

INTRODUCTION: Blood-based biomarkers (BBMs) have revolutionized Alzheimer's disease diagnosis and monitoring. Their pre-analytical stability requires scrutiny. This study assessed pre-analytical effects to inform a standardized sample handling protocol. METHODS: Assessed pre-analytical variations included collection tube type, hemolysis, centrifugation settings, centrifugation/storage delays, tube transfers, and freeze-thawing (n = 15/experiment). Phosphorylated tau (pTau) isoforms were measured with Simoa, Lumipulse, MesoScale Discovery, and immunoprecipitation-mass spectrometry. Amyloid-beta (Aβ42, Aβ40), glial fibrillary acidic protein (GFAP), and neurofilament light (NfL) protein were measured with Simoa. RESULTS: All assessed BBM levels varied by over 10% by collection tube type. Aβ peptides were the most sensitive, and their levels declined >by more than 10% under storage and centrifugation delays, more steeply at room temperature (RT) compared with 2°C to 8°C. NfL and GFAP levels increased by more than 10% upon RT/−20°C storage. pTau isoforms demonstrated stability across most pre-analytical variations. DISCUSSION: We established an evidence-based handling protocol to ensure reliable sample handling for neurological BBMs upon adoption in clinics, trials, and research. Highlights: Sample handling protocols can mitigate pre-analytical effects on BBM results. We developed an evidence-based, expert-consensus plasma sample handling protocol. Primary collection tube and delays to centrifuging or freezing impact AD BBMs. Plasma pTau217 is highly resistant to pre-analytical sample handling variations. Plasma Aβ42 and Aβ40 were most sensitive to pre-analytical variations.