A Randomised Prospective Crossover Study on the Effects of Medium Cut-Off Membranes on FGF-23 and Inflammatory Mediators in Patients Receiving Regular Haemodialysis

INTRODUCTION: In contrast to high-flux dialysis (HFD) membranes, medium cut-off membranes (MCO) can potentially remove a wide range of middle molecules. Our study aimed to compare the clearance rate (CR) of fibroblast growth factor 23 (FGF-23) and other selected inflammatory cytokines between medium MCO and HFD membranes and investigate the intrasubject stability of these biomarkers. METHODS: This prospective randomised case-crossover study recruited 20 adult patients who were randomised into two groups: group A: to start with 1 week of thrice-weekly dialysis using HFD membrane followed by a 3-week washout period and then 1 week of dialysis with an MCO membrane. Group B followed the reverse sequence. Blood samples were taken before and after each dialysis session for the analysis of the assessed biomarkers (FGF-23, interleukin-6 [IL-6], interleukin-18 [IL-18], high-sensitivity C-reactive protein [hsCRP], and dephosphorylated uncarboxylated matrix Gla protein [dp-ucMGP]). Wilcoxon signed rank and paired t tests were used for comparison between the membranes. One-way repeated measures ANOVA or Friedman tests were used for the intrasubject stability of the biomarkers. RESULTS: The use of both MCO and HFD membranes resulted in a significant reduction of FGF-23 levels and other selected inflammatory cytokines. However, there was no significant difference in the CR: FGF-23 (0.31 vs. 0.23], p = 0.242), IL-6 (0.19 vs. 0.12, p = 0.215), IL-18 (-0.05 vs. -0.03, p = 0.704), dp-ucMGP (0.33 vs. 0.33, p = 0.903), and hsCRP (-0.05 vs. -0.08, p = 0.107). There was no significant intrasubject variability for all assessed biomarkers except in pre-dialysis high hsCRP levels when using HFD membrane. CONCLUSION: The use of both MCO and HFD membranes resulted in a significant reduction of FGF-23 levels and other selected inflammatory cytokines. However, the MCO membrane did not demonstrate a significant advantage over the HFD in the short term. There was no significant intrasubject variability for all assessed biomarkers apart from hsCRP.