Delayed-centrifugation blood collection tube for remote blood biomarker assessment

Introduction: Plasma phosphorylated tau 217 (p-tau217) and amyloid-β 42 (Aβ42) are advancing toward clinical use for Alzheimer's disease (AD), but their reliability can be impacted by preanalytical handling. Although alternative collection tubes with distinct stabilization strategies —P100 (protease inhibitor) and HEMAcollect (hemolysis/platelet-activation minimization) —have been developed to stabilize plasma proteins, how well they preserve these markers remains unresolved; we therefore compared both against fresh standard EDTA tubes. Methods: In 40 participants, plasma p-tau217 and Aβ42 were measured (Lumipulse) in paired fresh EDTA, P100, and HEMAcollect samples after 5-day ambient storage. We assessed concentration change, rank-order preservation (Spearman ρ), percentage difference, and diagnostic classification under the p-tau217/Aβ42 ratio and p-tau217 alone. Results: P100 preserved p-tau217 favorably, with high rank-order correlation (ρ=0.98) and a modest median change (+12.1%), and its classification agreement with fresh EDTA reached 97.5% using p-tau217 alone. HEMAcollect showed greater p-tau217 signal loss (−57.5%). Aβ42 was reduced in both tubes (−72.8% P100; −95.5% HEMAcollect) with loss of rank order, so neither preserved the p-tau217/Aβ42 ratio. Discussion: Stability was tube- and analyte-specific, and P100 consistently outperformed HEMAcollect —preserving p-tau217 rank order while HEMAcollect reduced signal across analytes. Although neither tube preserved the Aβ42-dependent ratio, P100 shows potential for p-tau217-based workflows. Preanalytical stability must be established analyte by analyte before alternative tubes enter clinical AD diagnosis.