Effects of high albumin leakage on survival between online hemodiafiltration and super high-flux hemodialysis: the HISTORY study

Background All-cause mortality is lower with a high substitution volume in predilution (pre) and postdilution (post) online hemodiafiltration (OHDF) than with hemodialysis (HD), and mortality does not significantly differ between pre- and post-OHDF groups. Despite the improved survival with a high substitution volume, there may be limitations. On the other hand, either normoalbuminemia or high albumin leakage in HD can reduce mortality, and super high-flux (SHF) membrane dialyzers can reduce mortality compared with low-flux and high-flux membrane dialyzers. Here, we investigated the associations of serum albumin concentration (s-Alb), albumin leakage, and substitution volume with all-cause mortality in OHDF and SHF-HD. Methods In a 3-year retrospective observational study of patients receiving dialysis from April 1 to July 1, 2017, we developed a propensity score-matched model using 783 stable patients (SHF-HD, 355; OHDF, 428). We used the log-rank test to compare Kaplan-Meier survival curves and Cox regression analysis to calculate hazard ratio (HR). Cox regression analysis was also used to compare the effect of estimated albumin leakage (EAL) and substitution volume on 3-year all-cause mortality. Results All-cause mortality was significantly lower with high EAL than with low EAL (SHF-HD: P = 0.012, log-rank test; HR, 0.44; 95% confidence interval [CI] 0.23-0.85; OHDF: P = 0.027, log-rank test; HR, 0.41; 95% CI 0.18-0.93). The mortality of high EAL was not significantly different between high and low s-Alb in SHF-HD (3.5 [+ or -] 0.1 and 3.2 [+ or -] 0.2 g/dL) and OHDF (3.6 [+ or -] 0.2 and 3.2 [+ or -] 0.1 g/dL), despite significant differences in s-Alb. Mortality did not significantly differ between SHF-HD and OHDF with higher EAL ranges or a lower difference in EAL. Mortality in pre-OHDF was significantly correlated with EAL (P = 0.007, beta - 0.32) rather than substitution volume, and mortality in post-OHDF was not analyzed because of fewer deaths. Conclusions The results suggest that survival is improved more with high EAL than with low EAL in both OHDF and SHF-HD patients, that high EAL with mild-to-moderate hypoalbuminemia does not necessarily worsen survival in OHDF and SHF-HD patients, and that survival is equivalent between OHDF and SHF-HD patients with a similar level of EAL. Keywords: Albumin leakage, Hypoalbuminemia, Super high-flux hemodialysis, Online hemodiafiltration, Survival