Serum levels of beta-trace protein and its association to diuresis in haemodialysis patients

Background. Beta-trace protein (BTP) has been proposed as an alternative endogenous marker of the glomerular filtration rate. However, possible determinants of BTP in ESRD patients undergoing regular renal replacement therapy have not been evaluated. Methods. Serum levels of BTP, beta-2-microglobulin, creatinine and urea were analysed before and after dialysis treatment in 73 patients [ haemodialysis (HD) n = 52; haemodiafiltration (HDF) n = 21]. Patients were categorized into four groups with residual diuresis (RD) < 0.51/day (group 1; n = 24), 0.5-11/day (group 2; n = 18), 1.1-1.51/day (group 3; n = 12) and > 1.51/day (group 4; n = 19). Subsequently RD was compared to pre-treatment levels of BTP. Results. HD treatment did not affect BTP serum levels [pre-treatment 8.1 +/- 4.1 mg/l (mean+SD) vs post-treatment 7.7 +/- 4.1 mg/l; -0.6 +/- 16.1%; ns]. However, in 6 out of 21 patients undergoing HDF BTP levels were reduced by more than 20%. Overall, the resulting decrease in serum concentration was minuscule (9.6 +/- 6.2 vs 8.3 +/- 4.9 mg/l; -14 +/- 21.9%; P = 0.03). BTP serum levels were tightly associated to RD of the four groups. Comparison of BTP levels showed significant differences between patients of groups 1 vs 3 and 4 as well as 2 vs 4. Conclusions. BTP serum levels may serve as a surrogate marker for residual renal function since HD and HDF do not exert clinical relevant alterations on them. Furthermore, BTP serum concentrations appear strongly associated to RD.