Biochemical comparison of 8 h haemodialysis and 4 h haemodiafiltration, and two dialysis membranes, in a randomized cross-over trial

AIM: Extended-hours haemodialysis has long been regarded as the optimal form of dialysis for solute clearance. With emerging benefits of haemodiafiltration, we wanted to compare these two head-to-head. METHODS: In this randomized cross-over trial, we recruited existing nocturnal haemodialysis patients, who had not been hospitalized in the prior 3 months. After a baseline 8 h haemodialysis session, subjects were randomized to either 2 weeks of 8 h haemodialysis or 4 h haemodiafiltration with cross-over to the alternative treatment after a 2-week washout period. Subjects were additionally randomized to the Fresenius FX80 or Nipro Elisio in a parallel design. Blood and dialysate samples were collected at baseline and at the end of both study periods. RESULTS: Twelve patients completed the study. Mean (SD) age and body mass index were 55.1 ± 11.5 years and 36.4 ± 10.8, respectively. Urea and creatinine reduction ratios were higher with extended-hours haemodialysis compared to haemodiafiltration (difference 14.0%, 95% CI = 10.6, 17.3; P < 0.001 and 9.1%, 95% CI = 11.0, 7.2; P < 0.001). Fibroblast growth factor 23 (FGF23) clearance was superior with haemodiafiltration (difference 20.1%, 95% CI = 8.7, 31.6; P = 0.001). No difference was seen in reduction ratios for phosphate, retinol binding protein, alpha-1-microglobulin, beta-2-microglobulin and fetuin with both modalities. Compared to Nipro Elisio, Fresenius FX80 dialyser achieved higher beta-2-microglobulin clearance (Period 1: difference 7.8%, 95% CI = 1.3, 14.4; P = 0.02, Period 2:7.5%, 95% CI = 1.0, 14.1; P = 0.02). CONCLUSIONS: Small solute clearance was superior with extended-hours haemodialysis while haemodiafiltration enhanced FGF23 clearance. Beta-2-microglobulin clearance was improved with Fresenius FX80 dialyser, but this difference is unlikely to be clinically significant.