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ISO 10993-4 in vivo thrombogenicity testing is frequently performed for regulatory approval of many blood-contacting medical devices and is often a key part of submission packages. Given the current state of in vivo thrombogenicity assays, a more robust and reproducible assay design, including in vitro models, is needed. This study describes an in vitro assay that integrates freshly harvested ovine blood containing minimal heparin in a closed pumped loop. To confirm the reproducibility of this assay, control materials were identified that elicited either a positive or a negative thrombogenic response. These controls demonstrated reproducibility in the resulting thrombogenicity scores with median scores of 5 and 0 for the positive and negative controls, respectively, which also demonstrated a significant difference (p

The purpose of this test method is to assist in the determination of the thrombogenic potential of medical materials exposed to human whole blood. By evaluating surface-induced activation, platelet adherence to a material, and platelet and leukocyte depletion from blood, a material’s potential for thrombus formation can be assessed. If a significant decrease in platelets and/or leukocytes is observed in whole blood when compared to a blank control, the tested material has the potential to induce an in-vivo thrombogenic response. The present standard for the testing of platelet and leukocyte response to cardiovascular materials, ASTM F2888-13, Standard Test Method for Platelet Leukocyte Count - An In-Vitro Measure for Hemocompatibility Assessment of Cardiovascular Materials [1], mandates the use of several reference materials in the presence of blood anticoagulated with sodium citrate. This study was designed to address the relevance of the assay method when using a potent anticoagulant, 3.2% sodium citrate, to evaluate the thrombogenic potential of medical devices. Current studies on this question are under investigation at the FDA also with the intent of improving the standard methods for this assay by evaluating blood anticoagulated with 2–3 IU/mL of heparin [2]. For this study, the effects of several biomaterials were evaluated when exposed to blood anticoagulated with sodium citrate and, concurrently, an even lower dose of heparin at 1 IU/mL also used by our laboratory in a new circulating in vitro assay for thrombogenicity [3]. We believe this test method allows for a sensitive assay that can more accurately predict potential thrombogenic outcomes of cardiovascular materials, while maintaining appropriate responses in both positive and negative control materials.