CONTRAST study and TURKISH HDF study: Hemodiafiltration reduces mortality only if high substitution volumes are used

The issues as to which detoxification processes produce the best results in which patients and to what extent further optimisation is feasible are being investigated and debated repeatedly. HDF may possibly have advantages. No less than two new studies address this issue. One compared HDF with standard small pore HD; the other compared HDF with large pore HD.

The prospective, randomised CONTRAST study (1) aimed to evaluate whether treatment with HDF reduces overall mortality compared with low-flux HD. 714 prevalent patients were randomized to HDF or small pore HD. The median follow-up period was 3 years. In the outcome there was no difference between the two groups regarding the incidence of overall mortality (121/1000 person-years for online HDF versus 128/1000 for low-flux HD [HR 0.91, 95% CI 0.7 - 1.17]). However, a subgroup analysis indicated that patients who had reached a substitution volume of over 20 litres/treatment had a significantly lower mortality risk than patients with lower substitution volumes (HR 0.66; p = 0.03).

The prospective, randomised, controlled TURKISH HDF study (2) compared HDF with large pore hemodialysis (HD) in terms of morbidity and mortality. 782 patients were enrolled who had so far been given HD three times a week. They were randomised 1:1. The difference in terms of mortality was not significant (p = 0.28). Also the secondary end points (morbidity parameters) manifested no significant difference. In the subgroup analysis it was evident that HDF patients with a high substitution volume of > 17.4 L per treatment had a significantly better cardiovascular and overall survival rate compared to HDF patients with a lower substitution volume and compared to HD patients (p = 0.002). In the adjusted Cox analysis, HDF with a high substitution volume compared to high-flux HD was associated with a 46% reduction in the overall mortality risk and with a 71% reduction in cardiovascular mortality.

In conclusion it can be stated that with these two studies it has been possible for the first time to demonstrate prospectively that just "high-volume HDF" can reduce mortality, be it with subgroup or secondary analysis, which gives a lower strength of evidence.
(1) ONLINE HEMODIAFILTRATION VERSUS LOW-FLUX HEMODIALYSIS: EFFECTS ON ALL-CAUSE MORTALITY AND CARDIOVASCULAR EVENTS IN A RANDOMIZED CONTROLLED TRIAL. THE CONVECTIVE TRANSPORT STUDY (CONTRAST). Grooteman M, Van den Dorpel R, Bots M et al. Abstract No. 2507

(2) COMPARISON OF POSTDILUTION ONLINE HEMODIAFILTRATION AND HEMODIALYSIS (TURKISH HDF STUDY). Ok E, Asci G, Ok ES et al. Abstract No. 2506