Role of residual kidney function and convective volume on change in β2-microglobulin levels in hemodiafiltration patients

Background and objectives: Removal of β2-microglobulin (β2M) can be increased by adding convective transport to hemodialysis (HD). The aim of this study was to investigate the change in β2M levels after 6-mo treatment with hemodiafiltration (HDF) and to evaluate the role of residual kidney function (RKF) and the amount of convective volume with this change. Design, setting, participants, & measurements: Predialysis serum β2M levels were evaluated in 230 patients with and 176 patients without RKF from the CONvective TRAnsport STudy (CONTRAST) at baseline and 6 mo after randomization for online HDF or low-flux HD. In HDF patients, potential determinants of change in β2M were analyzed using multivariable linear regression models. Results: Mean serum β2M levels decreased from 29.5 ± 0.8 (±SEM) at baseline to 24.3 ± 0.6 mg/L after 6 mo in HDF patients and increased from 31.9 ± 0.9 to 34.4 ± 1.0 mg/L in HD patients, with the difference of change between treatment groups being statistically significant (regression coefficient -7.7 mg/L, 95% confidence interval -9.5 to -5.6, P < 0.001). This difference was more pronounced in patients without RKF as compared with patients with RKF. In HDF patients, β2M levels remained unchanged in patients with GFR >4.2 ml/min/1.73 m2. The β2M decrease was not related to convective volume. Conclusions: This study demonstrated effective lowering of β2M levels by HDF, especially in patients without RKF. The role of the amount of convective volume on β2M decrease appears limited, possibly because of resistance to β2M transfer between body compartments. Copyright

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