*Novel Capillary Whole Blood Collection Stakeholder Workshop Series

Capillary whole blood is a physiologically distinct and complex matrix, consisting of a mixture of arteriolar, capillary, and venular blood combined with variable amounts of interstitial and intracellular fluid. Because of this, biomarker concentrations in capillary blood can differ meaningfully from those in venous blood, which is the most characterized sample for reporting laboratory results. Novel capillary collection devices are being developed targeting alternate collection sites (e.g., arm). However, a critical and unresolved scientific gap exist, as it has not been established that capillary blood collected from the arm (or other body sites beyond the finger) produces results equivalent to venous samples across analytes. This gap is the primary barrier preventing the field of micro-sampling and home self-collection from advancing.Compounding this, are additional technical challenges, including small and variable sample volumes, the need to validate performance across diverse lay users (varying age, literacy, dexterity, and visual acuity), and real-world environmental variables in home settings such as poor lighting, temperature extremes during shipping, and lack of sterile surfaces.FDA/OHT7 proposes to convene 2-3 stakeholder workshops in FY2027 bringing together blood collection device manufacturers, assay developers, clinical laboratories, academic researchers, and patient representatives. The workshops would:Build shared scientific understanding of capillary collected from alternative sites vs. venous sample differencesPrioritize analytes and clinical use cases most in need of equivalency dataDevelop consensus on study designs, statistical approaches, and acceptance criteriaIdentify actionable steps for each stakeholder groupExplore collaborative or multi-site study coordination mechanisms