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Criteria and Principles of in vitro Hemocompatibility Testing according to the ISO 10993(4)

The development of synthetic materials and textured polymers and their increasing use in medicine make research of biomaterials’ hemocompatibility very relevant. Problems arise from the polymorphism and diversity of the different materials, the static and dynamic test models, and the patients’ individual biological factors. First, methods, models, tests as well as preanalytical 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 (Bundesärztekammer). The routine controls used in clinical chemistry and hematology have to be performed. Information about normal ranges (mean value, standard deviation, 95% confidence interval) should be provided. Tests have to 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 and the Chandler system. Quality and aspects of hemocompatibility such as platelet activation, oxidative burst, hemolysis, fibrinolysis, fibrin formation, generation of thrombin, contact activation, and complement activation were analyzed, and the results were entered into a nondimensional score system, where 0 points stand for the best and 65 points for the worst evaluation. In a low shear stress system, we found good correlations between the total score and i) contact activation, ii) thrombin generation and iii) leukocyte activation; in a high shear stress system good correlations were demonstrated 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 efficient diagnostic approach to hemocompatibility that takes account of clinical and socioeconomic concerns.