Paired Capillary and Venous Serum Specimen Agreement for Protein Biomarker Measurements and Risk Category Outputs in...

Background: Capillary blood sampling may improve access to multi-cancer early detection (MCED) by enabling less invasive and more decentralized specimen collection. However, its paired-specimen measurement agreement with conventional venous blood for protein biomarker-based MCED testing requires validation. Objective: The objective of this study was to evaluate agreement between capillary and venous blood specimens for OneTest protein biomarkers and to assess the exact risk category agreement of the OneTest Premium algorithm outputs generated from both specimen types. Methods: This two-stage study compared paired venous and capillary blood specimens. Study 1 enrolled 143 Taiwanese adults undergoing clinically indicated biomarker testing to evaluate paired-specimen measurement agreement. Study 2 involved an exploratory paired-specimen evaluation in 13 asymptomatic U.S. volunteers using an upper arm capillary blood collection device. Biomarker concentrations were compared using paired statistical testing, correlation analysis, and Bland-Altman analysis. OneTest Premium risk categories and cancer type prediction outputs were compared between specimen types. Results: In Study 1, no statistically significant differences were observed between capillary and venous specimens for any evaluated biomarker. Descriptive scatterplots showed strong linear associations between paired capillary and venous biomarker measurements across the observed concentration ranges. Bland-Altman analysis showed mean biases close to zero for most biomarkers, with biomarker-specific limits of agreement. In Study 2, all 12 biomarkers were successfully measured in all 13 participants. OneTest Premium risk categorization was concordant in 11 of 13 participants; discordant cases involved adjacent low-risk and mild-risk categories, with no major or very major classification errors. Given the small sample size, these findings are descriptive and preliminary. Conclusions: Capillary blood specimens showed paired measurement agreement with venous specimens in Study 1. The exploratory findings from Study 2 suggest that capillary-derived measurements may support the generation of OneTest Premium outputs.