Medium Cut-Off Dialyzer versus Eight Hemodiafiltration Dialyzers: Comparison Using a Global Removal Score

Background: A novel class of membranes, medium cut-off (MCO) membranes, has recently been designed to achieve interesting removal capacities for middle and large middle molecules in hemodialysis (HD) treatments. The few studies published to date have reported contradictory results regarding middle-sized molecules when comparing MCO dialyzers versus dialyzers used in online hemodiafiltration (OL-HDF). Methods: A prospective, single-center study was carried out in 22 patients. Each patient underwent 9 dialysis sessions with routine dialysis parameters, one with an MCO dialyzer in HD and the other 8 with different dialyzers in OL-HDF. The removal ratio (RR) of urea, creatinine, β 2 -microglobulin, myoglobin, prolactin, α 1 -microglobulin, α 1 -acid glycoprotein, and albumin was intraindividually compared. Albumin loss in dialysate was measured. We propose a global removal score ([urea RR + β 2 -microglobulin RR + myoglobin RR + prolactin RR + α 1 -microglobulin RR + α 1 -acid glycoprotein RR ]/6 – albumin RR ) as a new tool for measuring dialyzer effectiveness. Results: No significant differences in the RRs of small and middle molecular range molecules were observed between the MCO vs. OL-HDF dialyzers (range 60–80%). Lower RRs were found for α 1 -microglobulin and α 1 -acid glycoprotein without significant differences. The albumin RR was < 11% and dialysate albumin loss was < 3.5 g in all situations without significant differences. The global removal score was 54.9 ± 4.8% with the MCO dialyzer without significant differences. Conclusions: Removal of a wide range of molecular weights, calculated with the proposed global removal score, was almost equal with the MCO dialyzer in HD treatment compared with 8 high-flux dialyzers in high-volume OL-HDF without relevant changes in albumin loss. The global removal score could be a new tool to evaluate the effectiveness of dialyzers and/or different treatment modalities.