Investigation of dialyzer thrombogenicity is a critical step during the development of a new dialyzer. Novel dialyzer membranes aim to reduce the inherent thrombogenic potential of artificial surfaces by, e.g., increasing membrane hydrophilicity. Reliable in vitro testing is fundamental during dialyzer development and must be in line with the current standards. Using the novel FX CorAL dialyzer with its increased membrane hydrophilicity as an example, this study characterizes dialyzer thrombogenicity in an in vitro test setup in line with ISO 10993-4 and identifies factors which influence dialyzer thrombogenicity. In a recirculation setup with human blood, platelet activation (platelet counts, β-thromboglobulin, platelet adsorption), coagulation (thrombin–antithrombin III complex) and complement activation (sC5b-9) were investigated among polysulfone- (FX CorAL, FX CorDiax, Optiflux, xevonta), polyethersulfone- (ELISIO, Revaclear, Theranova) and AN69 ST-based (Nephral) dialyzers. Additionally, the impact of dialysate and electrolyte composition on thrombogenicity was investigated. The FX CorAL showed the lowest platelet activation compared to all poly(ether)sulfone-based dialyzers and lower complement activation compared to most poly(ether)sulfone-based dialyzers and to the Nephral dialyzer. No significant differences were observed between the investigated dialyzers with regard to plasmatic coagulation. Among the tested parameters, the dialyzer showed the strongest impact on the thrombogenicity results. This study proposes guidance on in vitro testing of dialyzer thrombogenicity in line with current standards and may contribute to reducing the current heterogeneity among in vitro hemocompatibility testing.

Performance and hemocompatibility are the main focus areas in the development of new hemofilters for continuous kidney replacement therapy. The novel multiFlux hemofilter features a polysulfone membrane with increased hydrophilicity to improve performance stability and hemocompatibility. In the present in vitro study, we compared the multiFlux hemofilter to established hemofilters on the market, i.e., Ultraflux AV (polysulfone-based), Prismaflex HF (polyarylethersulfone-based) and Prismaflex ST (AN69 ST-based). For the characterization of performance, dialysate-side plasma clearance of urea, creatinine and β2-microglobulin (β2M) were investigated over 24 h. Hemocompatibility was characterized in a blood recirculation setup by determining activation of platelets, plasmatic coagulation, the complement system and leukocytes. For urea and creatinine clearance, all hemofilters reached or approached the effluent limit across all time points. For β2M, the multiFlux hemofilter showed significantly higher clearance values at each time point vs. all comparators (p < 0.001) and the most stable performance over 24 h. The multiFlux hemofilter also showed a favorable hemocompatibility profile, especially in terms of platelet activation (vs. Ultraflux AV and Prismaflex HF) and complement activation (vs. all comparators). This in vitro study supports previous findings that increased membrane hydrophilicity improves performance stability and hemocompatibility of synthetic membranes.