Mortality reduction by post-dilution online-haemodiafiltration: a cause-specific analysis

Background: From an individual participant data (IPD) meta-analysis from four RCTs, comparing HD with online-HDF (ol-HDF), previously it appeared that HDF decreases all cause mortality by 14% (25;1) and fatal cardiovascular disease (CVD) by 23% (39; 3). Significant differences were not found for fatal infections and sudden death. So far, it is unclear, however, whether the reduced mortality risk of HDF is only due to a decrease in CVD events and if so, which CVD in particular is prevented, if compared to HD. Methods: The IPD-base was used for the present study. HRs and 95% CIs for cause specific mortality overall and in tertiles of the convection volume were calculated using the Cox Proportional hazard regression models. Annualized mortality and numbers needed to treat (NNT) were calculated. Results: Besides 554 patients dying from CVD, fatal infections and sudden death, 215 participants died from ‘other causes’, such as withdrawal from treatment and malignancies. In this group, the mortality risk was comparable between HD and ol-HDF patients, both overall and in tertiles of the convection volume. Subdivision of CVD mortality in fatal cardiac, non-cardiac and unclassified CVD, showed that ol-HDF was only associated with a lower risk of cardiac casualties [0.64(0.61;0.90)]. Annual mortality rates also suggest that the reduction in CVD death is mainly due to a decrease in cardiac fatalities, including both ischemic heart disease and congestion. Overall, 32, respectively 75 patients need to be treated by high volume HDF (HV-HDF) to prevent one all cause, respectively CVD death/year. Interpretation: The beneficial effect of ol-HDF on all cause and CVD mortality appears mainly due to a reduction in fatal cardiac events, including ischemic heart disease as well as congestion. In HV-HDF the NNT to prevent one CVD death is 75/year