Kinetics of β-2-Microglobulin with Hemodiafiltration and High-Flux Hemodialysis

Key Points Addition of hemodiafiltration has a relatively small impact on reducing either predialysis or time-averaged serum β -2-microglobulin levels. Residual kidney function has a major impact on the predialysis and time-averaged serum β -2-microglobulin levels. Background A kinetic model for β -2-microglobulin removal and generation was used to explore the impact of adding hemodiafiltration on predialysis and time-averaged serum values. Methods The model was tested on data from the HEMO study and on a sample of patients undergoing high-flux hemodialysis. The impact of hemodiafiltration on β -2-microglobulin levels was evaluated by modeling four randomized studies of hemodiafiltration versus hemodialysis. The impact of residual kidney function on β -2-microglobulin was tested by comparing results of previously reported measured data with model predictions. Results In the low-flux and high-flux arms of the HEMO study, measured median β -2-microglobulin reduction ratios could be matched by dialyzer clearances of 5.9 and 29 ml/min, respectively. Median predialysis serum β -2-microglobulin levels were matched if generation rates of β -2-microglobulin were set to approximately 235 mg/d. In another group of patients treated with dialyzers with increased β -2-microglobulin clearances, measured cross-dialyzer clearances (57±28 ml/min) were used as inputs. In these studies, the kinetic model estimates of intradialysis and early postdialysis serum β -2-microglobulin levels were similar to median measured values. The model was able to estimate the changes in predialysis serum β -2-microglobulin in each of four published randomized comparisons of hemodiafiltration with hemodialysis, although the model predicted a greater decrease in predialysis serum β -2-microglobulin with hemodiafiltration than was reported in two of the studies. The predicted impact of residual kidney clearance on predialysis serum β -2-microglobulin concentrations was similar to that reported in one published observational study. Modeling predicted that postdilution hemodiafiltration using 25 L/4 hours replacement fluid would lower serum time-averaged concentration of β -2-microglobulin by about 18.2%, similar to the effect of 1.50 ml/min residual kidney GFR. Conclusions A two-pool kinetic model of β -2-microglobulin yielded values of reduction ratio and predialysis serum concentration that were consistent with measured values with various hemodiafiltration and hemodialysis treatment regimens. Podcast This article contains a podcast at https://www.asn-online.org/media/podcast/CJASN/2024_08_01_CJASNJuly197812024.mp3