**3. Efficacy of online hemodiafiltration**

Several studies have shown online hemodiafiltration (OL-HDF) to be superior to conventional hemodialysis in reducing all-cause mortality in hemodialysis patients. OL-HDF has been found to reduce cardiovascular events as compared with conventional hemodialysis.

Furthermore, OL-HDF has significantly improved patients' satisfaction and quality of life [13– 16]. OL-HDF has also shown to be a cost-effective treatment for ESRD [17]. For example, in the prospective Convective Transport Study (CONTRAST), there was no significant difference between treatment groups with regard to all-cause mortality (121 versus 127 deaths per 1000 person-years in the OL-HDF and LF-HD groups, respectively); (hazard ratio, 0.95; 95% confidence interval, 0.75–1.20) after a mean follow-up of 3 years (range 0.4–6.6 years). Receiv‐ ing high-volume hemodiafiltration during the trial was associated with lower all-cause mortality.

In the ESHOL multicentre, open-label RCT [14], patients on OL-HDF compared with those on HD had a 55% lower risk of infection-related mortality (HR, 0.45; 95% CI, 0.21–0.96; *P* = 0.03), a 33% lower risk of cardiovascular mortality (HR, 0.67; 95% CI, 0.44–1.02; *P* = 0.06), and a 30% lower risk of all-cause mortality (**HR**, 0.70; 95% confidence interval [95% CI], 0.53–0.92; P = 0.01). In conclusion, high-efficiency post-dilution OL-HDF reduces all-cause mortality compared with conventional hemodialysis. According to the Turkish OL-HF prospective RCT [15], 782 patients undergoing thrice-weekly HD were enrolled and randomly assigned in a 1:1 ratio to either postdilution OL-HDF or high-flux HD. Using a filtration volume of 17.2 ± 1.3 **L, there** was no difference in the primary outcome between the two groups (event-free survival of 77.6% in OL-HDF vs. 74.8% in the high-flux group, *P* = 0.28). Also, no difference was seen in the cardiovascular and overall survival, number of hypotensive episodes and hospitaliza‐ tion rate. However on further analysis, the patients who received higher substitution volume (>17.4 L per session) had better cardiovascular outcome (*P =* 0.002) and overall survival (*P* = 0.03) compared with those who received high-flux HD. The study of Karkar et al. [16] aimed to investigate the effect of OL-HDF versus high-flux HD (HF) on a patient's healthrelated satisfaction level. A higher satisfaction level was achieved by the OL-HDF group compared with HF group (*p* < 0.0001). In the OL-HDF group, there was less itching (9 ± 10 vs. 48 ± 10), less cramps (3 ± 5 vs. 55 ± 8), less joint pain and stiffness (24 ± 10 vs. 83 ± 8) with improvement in sexual performance (57 ± 10 vs. 5 ± 5), social activity (82 ± 9 vs. 15 ± 8), and general mood (94 ± 9 vs. 28 ± 16). High-efficiency postdilution online HDF versus high-flux HD significantly improved patients' satisfaction and quality of life, including social, physical, and professional activities.
