Development of a large diameter in vitro flow loop thrombogenicity test system

Abstract Background To accommodate a wider range of medical device sizes, a larger in vitro flow loop thrombogenicity test system using 9.5 ‐mm inner diameter (ID) tubing was developed and evaluated based on our previously established 6.4 ‐mm ID tubing system. Methods Four cardiopulmonary bypass roller pumps were used concurrently to drive four flow loops during testing. To ensure that each pump produced a consistent thrombogenic response for the same material under the same test conditions, a novel dynamic roller occlusion setting method was applied. Five materials with varying thrombogenic potentials were tested: polytetrafluoroethylene (PTFE), silicone, 3D‐printed nylon, latex, and nitrile rubber (BUNA). Day‐old bovine blood was heparinized to a donor‐specific concentration and recirculated through the flow loops containing test materials at 20 rpm for 1 h at room temperature. Material thrombogenicity was characterized by measuring the thrombus surface coverage, thrombus weight, and platelet (PLT) count reduction. Results The larger tubing system can differentiate thrombogenic materials (latex, BUNA) from the thromboresistant PTFE material. Additionally, silicone and the 3D‐printed nylon exhibited an intermediate thrombogenic response with significantly less thrombus surface coverage and PLT count reduction than latex and BUNA but more thrombus surface coverage than PTFE ( p < 0.05). Conclusion The 9.5 ‐mm ID test system can effectively differentiate materials of varying thrombogenic potentials when appropriate pump occlusion settings and donor‐specific anticoagulation are used. This system is being assessed in an interlaboratory study to develop standardized best practices for performing in vitro dynamic thrombogenicity testing of medical devices and materials.