Removal of free light chains in hemodialysis patients without multiple myeloma: a crossover comparison of three different dialyzers

Background: Immunoglobulin light chains are classified as middle molecule uremic toxins able to interact with B lymphocyte membranes leading to the activation of transmembrane signaling. The ensuing impairment of neutrophil function can contribute to the chronic inflammation state of uremic patients, and the increased risk of bacterial infections or vascular calcifications. The aim of this crossover observational study was to assess the difference in free light chain removal by three different hemodialysis filters in patients not affected by multiple myeloma. Methods: Free light chain removal was compared in the polymethylmethacrylate (PMMA) membrane Filtryzer BK-F, the polyphenylene HFR17 filter and the conventional polysulfone filter F7HPS. Twenty chronic hemodialysis patients were enrolled: mean age was 67.7 +/- 17.0 years, M/F = 14/6, dialysis vintage (months) 25.5 +/- 32.0. The patients were randomized into two groups of treatment lasting 6 weeks each. The dialysis sessions checked were the midweek sessions and the blood was drawn at times 0, 120' and 240'. Kappa (k) and lambda (lambda) light chain levels, beta 2microglobulin (beta 2M), C reactive protein (CRP) and albumin were checked. Results: K light chain levels were 345.0 +/- 100.0 mg/L, lambda light chains were 121.4 +/- 27.0 mg/L. The values of k light chains at times 120' and 240' were significantly lower with PMMA and HFR17 than those obtained with F7. The reduction ratio per session (RRs) for k light chains was 44.1 +/- 4.3% with HFR17, 55.3 +/- 3.4% with PMMA, 25.7 +/- 8.3% with F7 (p = 0.018). The RRs for lambda light chains was 30.3 +/- 2.9% with HFR17, 37.8 +/- 17.3% with PMMA, 14.0 +/- 3.9% with F7 (p = 0.032). As to beta 2M, RRs was 42.4 +/- 3.2% with HFR17 vs. 33.9 +/- 2.8% with PMMA vs. 6.3 +/- 1.9% with F7 (p = 0.022). The three filters tested showed no differences in CRP or albumin levels. Conclusion: In terms of light chain and beta 2M removal, the PMMA and on-line HFR filters are similar and both are significantly more effective than the F7 filter in chronic dialysis patients.