Current Evidence in Haemodiafiltration.

Background: Standard low-flux haemodialysis (HD) is not very efficacious, and patient morbidity and mortality rates are still very high. According to the initial study design, the MPO study reported that high-flux HD (hf-HD) showed a significant 37% relative risk reduction of mortality in patients with serum albumin ≤4 g/dl; online haemodiafiltration (HDF) is considered the most efficient technique of using high-flux membranes, as clearances of small solutes, like urea, are higher than in haemofiltration and clearances of middle solutes, like β2-microglobulin, are higher than in hf-HD.

Summary: Three randomized trials have recently been published analysing the effect of online HDF on mortality. Two trials were unable to demonstrate a positive effect of HDF on survival, while 1 showed a significantly better survival in patients randomized to HDF in comparison to those randomized to hf-HD. It is intriguing that post hoc analyses of these 3 studies showed that the patients randomized to online HDF who received the highest convection volumes had a lower risk of mortality and cardiovascular events than those randomized to HD. Four very recently published meta-analyses have shown inconsistent results concerning the effect of convective treatments in improving patient general and cardiovascular survival, while they have consistently shown a significant reduction of the intradialytic symptomatic hypotension in patients treated with convective techniques in comparison with those treated with prevalent diffusive ones. Key Messages: The results of the randomized trials on the effect of HDF in improving patient survival are inconclusive. Moreover, trials specifically designed for testing the effect of increased convection of online HDF on patient survival and morbidity in comparison to patients treated with hf-HD are still awaited.