Feasibility and validity of using self-collected capillary blood using Tasso+ for measuring Alzheimer's Disease plasma-based biomarkers among underrepresented populations

BackgroundBlood-based biomarkers offer a scalable alternative to cerebrospinal fluid and PET imaging for Alzheimers disease (AD) detection, yet traditional venipuncture limits participation among rural and socioeconomically disadvantaged populations. Self-collection using the Tasso+ capillary device could reduce access barriers, but its feasibility and validity for AD plasma biomarkers remain uncertain, particularly with real-world delays prior to processing. MethodsAdults aged 45-90 years from the Wisconsin SHOW cohort who were underrepresented in AD research (Black or Hispanic race/ethnicity, rural residence, or <bachelors degree) were recruited (n=28). At community "pop-up" clinics participants completed: (1) self-collection of capillary blood via Tasso+; (2) experience surveys; (3) Montreal Cognitive Assessment; and (4) standard venipuncture. To simulate home-based collection and mail return, Tasso+ samples were held at room temperature for 24 hours before centrifugation, whereas venous samples were processed within 30 minutes. Plasma A{beta}40, A{beta}42, A{beta}42/40, GFAP, NfL, and pTau217 were measured on the Quanterix Simoa platform. Between-method agreement was evaluated using Pearson/Spearman correlations, Lins concordance correlation coefficients (CCC), Bland-Altman analyses, and relative bias. Predictors of percent difference were explored with univariate regression. ResultsTasso+ collection was successful for 96% of participants; 64% rated it very easy and 86% reported comfort/no pain, yet 57% preferred future venipuncture--particularly Black, lower-income, and lower-education participants. Agreement varied markedly by biomarker. GFAP and NfL demonstrated excellent concordance (CCC 0.97-0.98) with minimal bias (-6% to -8%). A{beta}40 and A{beta}42 showed modest correlations (r=0.40-0.47) and substantial underestimation (-60% to -70%). A{beta}42/40 and pTau217 exhibited poor correlation and extreme positive bias for pTau217 ([~]+2600%). Hemolysis was more frequent in Tasso+ samples and contributed to disagreement for several markers; processing lag and sample volume were not strong predictors. ConclusionsRemote capillary self-collection with a 24-hour delay is suitable for measuring GFAP and NfL but not currently reliable for A{beta} or pTau217 without improved handling (e.g., temperature control, hemolysis reduction). Although user experience was favorable, trust and logistical concerns limited preference among underrepresented groups. Community-informed strategies and optimized pre-analytics are essential before deploying Tasso+ in large AD studies.