The Medium Cut-Off Membrane Does Not Lower Protein-Bound Uremic Toxins

The accumulation of protein-bound uremic toxins (PBUT) is associated with increased cardiovascular outcomes in patients on dialysis. However, the efficacy of PBUT removal for a medium-cutoff (MCO) membrane has not been clarified. This study was designed to assess the efficacy of PBUT clearance according to dialysis modalities. In this prospective and cross-over study, we enrolled 22 patients who received maintenance hemodiafiltration (HDF) thrice weekly from three dialysis centers. The dialysis removal of uremic toxins, including urea, beta 2-microglobulin (B2MG), lambda free light chain (λ-FLC), indoxyl sulfate (IS), and p-cresyl sulfate (pCS), was measured in the 22 patients on high-flux HD (HF-HD), post-dilution online HDF (post-OL-HDF), and MCO-HD over 3 weeks. The average convection volume in post-OL-HDF was 21.4 ± 1.8 L per session. The reduction rate (RR) of B2MG was higher in post-OL-HDF than in MCO-HD and HF-HD. The RR of λ-FLC was the highest in MCO-HD, followed by post-OL-HDF and HF-HD. The dialysate albumin was highest in MCO-HD, followed by post-OL-HDF and HF-HD. Post-dialysis plasma levels of IS and pCS were not statistically different across dialysis modalities. The total solute removal and dialytic clearance of IS and pCS were not significantly different. The clearance of IS and pCS did not differ between the HF-HD, post-OL-HDF, and MCO-HD groups.