Platelet and leukocyte count assay for thrombogenicity screening of biomaterials and medical devices: Evaluation and improvement of ASTM F2888 test standard.

An appropriate preclinical thrombogenicity evaluation of a blood-contacting device is important to reduce thrombosis and thromboembolism risks to patients. The in vitro platelet and leukocyte count assay, as described in the ASTM F2888 test standard, aims to assess thrombogenic potentials of blood-contacting materials. The goals of this study were to evaluate whether this standardized test method can effectively differentiate materials with different thrombogenic potentials and to investigate the impact of anticoagulation conditions on test sensitivity. Using human blood with various anticoagulation conditions, we performed the platelet and leukocyte count assays on four biomaterials and three positive control materials. We found that the use of sodium citrate anticoagulation as stipulated in the 2013 version of the ASTM F2888 standard cannot differentiate materials with different thrombogenic potentials. The modification to use low-concentration heparin, either with recalcified citrated blood or with direct heparinization, substantially improved the test sensitivity and enabled the assay to distinguish platelet count reduction between the positive controls and commonly used biomaterials. Leukocyte count was shown to be a much less sensitive indicator than platelet count for thrombogenicity evaluations of biomaterials. The findings from this study have been incorporated in the recent 2019 version of the ASTM F2888 standard.