Super high-flux membrane dialyzers improve mortality in patients on hemodialysis: a 3-year nationwide cohort study

INTRODUCTION: In Japan, dialyzers are classified based on β(2)-microglobulin clearance. Type I dialyzers are classified as low-flux dialyzers (<10 mL/min clearance), type II and III as high-flux dialyzers (≥10 to <30 mL/min and ≥30 to <50 mL/min clearance, respectively), and type IV and V as super high-flux dialyzers (≥50 to <70 mL/min and ≥70 mL/min clearance, respectively). Super high-flux dialyzers are commonly used, but their superiority over low-flux dialyzers is controversial. METHODS: In this nationwide prospective cohort study, we analyzed Japanese Society for Dialysis Therapy Renal Data Registry data collected at the end of 2008 and 2011. We enrolled 242,467 patients on maintenance hemodialysis and divided them into five groups by dialyzer type. We assessed the associations of each dialyzer type with 3-year all-cause mortality using Cox proportional hazards models and performed propensity score matching analysis, adjusting for potential confounders. RESULTS: By the end of 2011, 53,172 (21.9%) prevalent dialysis patients had died. Mortality significantly decreased according to dialyzer type. Hazard ratios (HRs) were significantly higher for type I, II and III compared with type IV (reference) after adjustment for basic factors and further adjustment for dialysis-related factors. HR was significantly higher for type I, but significantly lower for type V, after further adjustment for nutrition- and inflammation-related factors. These significant findings were also evident after propensity score matching. CONCLUSIONS: Hemodialysis using super high-flux dialyzers might reduce mortality. Randomized controlled trials are warranted to clarify whether these type V dialyzers can improve prognosis.