The development of a novel device to aid in capillary macro blood self-sampling via an iterative study design.

Background: Blood sampling is essential for infectious disease diagnosis and monitoring but often requires venipuncture, limiting accessibility. Self-sampling offers a decentralized alternative, yet current macro-blood sampling methods are scarce. The device was developed to enable standardized, user-friendly self-sampling of ≥ 500 µL capillary fingerprick blood.

Research design and methods: Via an iterative, mixed-method approach, we optimized the Collect2Know device (C2K) across five prototypes (P1-P5). Usability, acceptability, and blood volume of each prototype were assessed among minimum 10 participants. A minimum threshold of 75% usability and acceptability, and 60% of users collecting minimum 500 µL guided device refinement.

Results: The first prototype (P1) underperformed, leading to redesign. P2-P3 improved usability and acceptability but failed volume collection targets. P4 incorporated substantial improvements, making the prototype more intuitive, and 77.5% (31/40) achieved success in blood collection with usability and acceptability scores of 89.1% and 75.6%, respectively.

Conclusions: This study highlights the value of an iterative study-design, in the early stages of device development. The C2K device will facilitate capillary fingerprick macro-bloodsampling. By shifting routine blood sampling to decentralized settings, the C2K device may have the potential to enhance access to diagnostics, reduce healthcare burdens, and support public health efforts in both high- and low-resource settings.