Objective: Low molecular mass proteins (LMMP) are putative uraemic toxins, but their elimination is negligible in standard haemodialysis (HD). In this study, we used beta(2)-microglobulin, cystatin C and beta-trace protein, which differ in molecular mass and charge, to characterize the elimination patterns of three different dialysis modalities.
Material and methods: Plasma samples were obtained at the start, 30 min after the start, at the end of the dialysis treatment and 30 min after termination of the dialysis session. Seventeen patients were treated with low-flux HD, 13 with post-dilution haemodiafiltration (HDF) and 8 with pre-dilution haemofiltration (HF). The changes in concentrations of the three LMMPs were monitored and expressed as percentages of the concentrations at the start of treatments.
Results: Conventional HD with low-flux membranes showed a high elimination of small molecules (urea and creatinine), but did not reduce the levels of the three LMMPs studied. During HDF and HF, there was a significant decrease in the plasma levels of cystatin C (to 28 % and 44 %, respectively) (p<0.001) and of beta(2)-microglobulin (to 23 % and 33 %, respectively) (p<0.001). However, the level of beta-trace protein was significantly reduced (to 65 %) only after HDF.
Conclusions: The three dialysis modalities showed significantly different elimination patterns for the LMMPs studied. Elimination of beta-trace protein was lower than those of cystatin C and beta(2)-microglobulin both in HDF and HF. beta-trace protein was only moderately eliminated by HDF and not at all by HF, and may be a useful marker in the evaluation of different convective therapies.