Improved micro-sampling methodology enables accurate platelet function analysis

Micro-sampling for platelet function assays offers a minimally invasive alternative to venipuncture that may facilitate point-of-care testing. We have developed a new micro-sampling methodology for human and mouse and evaluated these methods for platelet function analysis. Blood was collected by venepuncture or our new finger-prick sampling method in humans, and by terminal bleeding or a modified tail vein bleeding method in mice. Platelet activation was assessed by flow cytometry, measuring fibrinogen binding and P-selectin exposure in response to ADP, CRP-XL or TRAP-6 in humans (n = 14) and fibrinogen binding in response to ADP, CRP-XL in mice (n = 5). In humans, platelet sensitivity (EC₅₀) and capacity (maximal minus minimal response) showed no significant differences between capillary and venous samples, except for a higher EC₅₀ of P-selectin exposure to CRP-XL in capillary samples (0.179 µg/mL), compared to venous samples (0.026 µg/mL). This may be clinically relevant but requires further investigation. In mice, no significant differences were observed in EC₅₀ or capacity in response to ADP or CRP-XL between the terminal bleeding techniques and our modified tail vein method. Our new finger-prick sampling and tail vein bleeding methods are viable alternatives to the standard methods used for platelet function analysis. They maintain assay accuracy while improving accessibility and reducing and refining the use of animal models.