Protein-Bound Uremic Toxins Removal with MCO Membranes: A Pilot Study Showing No Superiority over High-Flux Dialysis

Background: Protein-bound uremic toxins such as advanced glycation end products (AGEs) are poorly cleared by conventional dialysis. Medium cut-off (MCO) membranes have been proposed to enhance their removal, but clinical evidence remains limited. Methods: In this prospective pilot study, eight maintenance hemodialysis patients were assigned to receive a single dialysis session using either an MCO or high-flux (HF) membrane. Serum levels of N-carboxymethyllysine (CML), soluble receptor for AGEs (sRAGE), and prolactin were measured pre- and post-dialysis. Reduction ratios corrected for hemoconcentration (RRc) were compared between groups. Results: The median RRc for CML was similar between MCO (36.9%) and HF (35.6%) membranes (p = 0.686). sRAGE reduction was lower with MCO membranes (21.8% vs. 41.9%, p = 0.114), while prolactin clearance was slightly higher (58.1% vs. 50.9%, p = 0.486). No statistically significant differences were observed. Conclusion: MCO membranes did not demonstrate superior removal of protein-bound toxins compared to high-flux membranes in this pilot study. These findings highlight the need for alternative strategies, such as adsorption, and larger studies to define the clinical utility of MCO technology.