Analytical validation of a novel capillary finger-stick blood sampling device for clinical chemistry, complete blood count, and hemoglobin A1c testing

Background and aims Capillary Cup® is a novel finger-stick blood collection device equipped with separation float technology to effectively isolate plasma and blood cell layers. This study aimed to evaluate its analytical equivalence compared to venipuncture sampling in clinical chemistry, complete blood count, and hemoglobin A1c testing. Methods Blood samples were collected from 63 healthy participants for clinical chemistry and hemoglobin A1c tests and 67 for complete blood count tests. Discrepancies between the Capillary Cup® and venipuncture sampling results were analyzed using the 2025 Clinical Laboratory Improvement Amendments (CLIA) acceptance limits and total allowable error (TE_A) thresholds. Results The Capillary Cup® samples showed strong linear correlations with venipuncture samples across proteins, transaminases, kidney function markers, lipids, C-reactive protein, blood cell and platelet counts, white blood cell differentials, hemoglobin, hematocrit, and Wintrobe's indices ( r = 0.740–0.999, P < 0.0001). Hemoglobin A1c was accurately measured alongside other clinical chemistry markers in a single kit ( r = 0.976, P < 0.0001). All values met the 2025 CLIA acceptance limits, and most also met the TE_A thresholds. Minor deviations were observed for creatinine, triglycerides, and C-reactive protein, as well as for platelet counts—potentially affected by activation and aggregation—but all remained within acceptance limits and demonstrated preserved linearity. Conclusions The Capillary Cup® provides analytically equivalent results to venipuncture for all tested parameters. It is easy to use, reduces waste, and is a potential alternative for at-home health monitoring, addressing challenges in venous access, and reducing iatrogenic blood loss risk in clinical practice.