Criteria and principles of in vitro hemocompatibility testing according tothe ISO 10993(4)

The development of synthetic materials and textured polymers and their incr easing use in medicine make research of biomaterials' hemocompatibility ver y relevant. Problems arise from the polymorphism and diversity of the diffe rent materials, the static and dynamic test models, and the patients' indiv idual biological factors. First, methods, models, tests as well as preanaly tical factors have to be standardized according to the current knowledge in medicine laid down in the ISO 10993(4) and in the guidelines given by the relevant German medical societies and the Federal Chamber of Physicians (Bu ndesarztekammer). The routine controls used in clinical chemistry and hemat ology have to be performed. Information about normal ranges (mean value, st andard deviation, 95% confidence interval) should be provided. Tests have t o be performed within a minimal delay of usually 2 h since some properties of blood change rapidly following collection. Various conditions (depending on the wall shear rate) were simulated within the centrifugation system an d the Chandler system. Quality and aspects of hemocompatibility such as pla telet activation, oxidative burst, hemolysis, fibrinolysis, fibrin formatio n, generation of thrombin, contact activation, and complement activation we re analyzed, and the results were entered into a nondimensional score syste m, where 0 points stand for the best and 65 points for the worst evaluation . In a low low shear stress system, we found good correlations between the total score and i) contact activation, ii) thrombin generation and iii) leu kocyte activation; in a high shear stress system good correlations were dem onstrated between the total score and i) thrombin generation, ii) hemolysis and iii) platelet activation. Furthermore, the effect of additives can be measured. The concepts presented underline the relevance/importance of an e fficient diagnostic approach to hemocompatibility that takes account of cli nical and socioeconomic concerns.