A simple in vitro screening test for blood compatibility of materials

An in vitro closed-cell kinetic blood-coagulation test was developed and used to evaluate the blood compatibility of materials. The test compares the clotformation rate on a test surface to that of a control material, Silastic. This method avoids anticoagulants, blood flow variations, and the exposure to air and other foreign surfaces. Eight pairs of cells are sequentially evaluated as to the weight of thrombus formed, the amount of unclotted blood, and the reduction in platelet count of the blood exposed to both the test materials and the control. These data are used to calculate a relative index whereby materials can be rated quantitatively as to the rate of clot formation on their surface. The order of decreasing clot formation on one group of materials studied was as follows: biolized (Imai et al., Trans. Amer. Soc. Artif. Int. Organs, 17, 6, 1973) poly (ether urethane), segmented polyurethane, formaldehyde-treated pericardium, Hydron, glutaraldehyde-treated pericardium, biolized natural rubber, Hexsyn, heparinized natural rubber, Silastic, and natural rubber. Urethane and aldehyde-treated natural tissue had a lower percentage of red thrombus formation. These results generally correlate with in vivo observations.