Relative importance of residual renal function and convection in determining beta-2-microglobulin levels in high-flux haemodialysis and on-line haemodiafiltration.

BACKGROUND: Convective blood purification improves beta(2)-microglobulin (beta(2)M) removal and may delay the onset of dialysis-related amyloidosis. We assessed the differential effects of high-flux haemodialysis (HD) and on-line haemodiafiltration (HDF) on plasma beta(2)M levels, given the enhanced convective capability of HDF.

METHODS: We measured pre-dialysis beta(2)M levels in 297 patients in a programme employing both high-flux HD and HDF, then analysed the relationship of beta(2)M to modality and other variables.

RESULTS: Independent determinants of plasma beta(2)M levels were residual renal function, age, HD vintage, and C-reactive protein load, but not the patient's predominant modality (high-flux HD or HDF). Patients with KRU levels <0.5 ml/min had significantly higher beta(2)M levels than patients with KRU between 0.5 and 1 ml/min.

CONCLUSIONS: Residual renal function is of overriding importance as a determinant of beta(2)M levels in HD patients and may supersede enhanced convective clearance by HDF. Beneficial effects extend to very low levels of residual renal function.