Analytical performance of a delayed-centrifugation blood collection tube for remote blood biomarker assessment

Current biobanking guidelines require in-person blood collection and immediate processing for Alzheimer's disease (AD) biomarker assessment. We recently reported that the P100 blood collection tubes containing protease inhibitors improve protein biomarker stability over delayed centrifugation periods. However, whether this comparability extends beyond a small set of biomarkers to the broad panels enabled by high-plex platforms has not been established. Here, we performed a head-to-head comparison of 127 neurodegeneration-related biomarkers in paired P100 vs. standard ethylenediaminetetraacetic acid (EDTA) plasma samples from n = 43 community-dwelling older adult participants using the NUcleic acid-Linked Immuno-Sandwich Assay (NULISA) proteomic technology. The NULISA assay demonstrated excellent technical reproducibility (intra- and inter-plate coefficients of variation [CVs] <10%). Biomarker levels in P100 and EDTA tubes were strongly correlated, with mean and median Spearman coefficients exceeding ρ = 0.8. Six conventional AD biomarkers showed strong P100-EDTA correlations (ρ > 0.8) with minimal mean differences and no significant proportional bias in Bland-Altman analysis, including plasma Aβ42, GFAP, MAPT, NEFL, p-tau181, and p-tau231, while p-tau217 showed a P100-EDTA correlation of ρ = 0.57. Two biomarker ratios (Aβ42/Aβ40 and p-tau217/Aβ42) also showed minimal bias with no proportional bias detected. Receiver operating characteristic analysis using amyloid status, assessed with positron emission tomography in a subset of participants, showed comparable classification performance between the two tube types, with classification concordance up to 92% and no significant DeLong differences for most (80%) biomarkers. These findings indicate that, on the NULISA platform, P100 tubes yield analytical and classification performance comparable to conventional EDTA tubes, supporting their use for blood-based neurodegeneration biomarker research where immediate sample processing is not feasible.