Background: Hemodiafiltration is becoming a preferred treatment modality for dialysis patients in many countries. The volume of substitution fluid delivered has been indicated as an independent mortality risk factor. The aim of this study is to compare patient survival on three different treatment modalities: high-flux hemodialysis, low-volume online HDF (oHDF) and high-volume oHDF.
Methods: Incident hemodialysis and oHDF patients treated in 13 NephroCare centers in Bosnia and Herzegovina, Serbia and Slovenia between January 1, 2007, and December 31, 2011, were included in this epidemiological cohort study. High-volume oHDF was defined as substitution volume higher than the median substitution volume infused, otherwise low-volume. Main predictor was treatment modality at baseline and in time-dependent model. Other predictors were age, gender, diabetes mellitus, cerebrovascular accident, arrhythmia, hemoglobin and C-reactive protein.
Results: Four hundred and forty-two patients were included in the study. Median substitution fluid volume was 20.4 L. Mean difference between the oHDF groups in substitution fluid volume was 8.3 ± 5.2 L [95 % confidence intervals (95 % CI) 7.1-9.5, p < 0.0001]. The unadjusted hazard ratios (HR) with 95 % CI compared to high-flux HD were 0.87 (0.5-1.5) for low-volume oHDF and 0.29 (0.13-0.63) for high-volume oHDF. After the adjustment for covariates, the HR for patients on low-volume oHDF remained statistically insignificant compared to high-flux HD (0.84; 95 % CI 0.46-1.53), while patients on high-volume oHDF showed a marked and significantly lower HR (0.29; 95 % CI 0.13-0.68) than patients on high-flux HD in baseline model. While this effect failed to reach significance in the time-dependent model (HR 0.477; 95 % CI 0.196-1.161), possibly due to an inadequate sample size here, the consistency of results in both models supports the robustness of the findings. After switching from high-flux hemodialysis to oHDF, mean hemoglobin and albumin levels did not change significantly. Mean erythropoietin resistance index (ERI) and erythropoiesis stimulating agents (ESA) consumption decreased significantly (p = 0.02, p = 0.03, respectively).
Conclusions: The median substitution volume used in these three countries for post-dilutional oHDF is 20.4 L. oHDF is associated with significant reductions in ERI and ESA consumption. Only high-volume oHDF is associated with improved survival compared to high-flux hemodialysis.