Beta-2 microglobulin clearance in high-flux dialysis and convective dialysis modalities: a meta-analysis of published studies

Background. Recent meta-analyses suggest that higher removal of beta-2 microglobulin (beta M-2) with either high-flux (HFD) dialysis or hemodiafiltration (HDF) may be associated with decreased total and cardiovascular mortality in dialysis patients. However, there are limited data about the performance of high flux dialyzers and/or convective therapies in removing beta M-2. Methods. This is a random effects meta-analysis and meta-regression of data extracted from randomized controlled trials and observational studies in hemodialysis, hemofiltration and HDF regarding the efficiency of high flux dialyzers to remove beta M-2. Studies were searched using ProQuest in SCOPUS, EMBASE andMEDLINE. Results. We included 69 studies from 1 January 2001 to 12 June 2017 on 1879 patients with 6771 available measurements. Average beta M-2 clearance was 48.75 mL/min [95% confidence interval (CI) 42.50-55.21] for conventional HF dialysis, and 87.06mL/min (95% CI 75.08-99.03) for convective therapies (hemofiltration and HDF) with substantial heterogeneity among studies [P (Q) <= 0.001]. Inmultivariable meta-regression analyses, we found significantly higher beta M-2 clearance for polyarylethersulfone dialyzers when used for HFD and polysulfone membranes in convective therapies. However, the mass of beta M-2 removed into the dialysate did not depend on membrane material. Adjusted dialysate-side (-22.279, 95% CI -9.8 to -34.757, P<0.001) beta M-2 clearances were significantly lower than whole blood clearances, suggesting that adsorption contributes substantially to beta M-2 removal. Higher Kuf, blood flow and substitution fluid rates but not dialysate flow rates were associated with statistically significant and clinically meaningful elevation in beta M-2 clearance from the body independent of the dialysis modality. Conclusions. Membrane composition and characteristics, modality (convective versus diffusive), blood flow rates and substitution fluid rates in HDF play a significant role in the efficient removal of beta M-2 from the body in both diffusive and convective dialysis.