Determinants of plasma beta 2 microglobulin concentration: possible relation to membrane biocompatibility

Beta 2 microglobulin (beta 2m) concentrations were measured by radioimmunoassay in the serum of haemodialysed patients. beta 2m was higher in males (n = 48) than in females (n = 26), i.e. 40.3 +/- 10.1 mg/l (SD) vs 31.2 +/- 8.0, P less than 0.01). beta 2m was not significantly higher in patients with bone cysts (37.7 +/- 11.4 mg/l vs 37.0 +/- 10.0), but median duration of dialysis was significantly (P less than 0.01) longer in patients with bone cysts (90 vs 57 months). beta 2m was lower in patients maintained on dialysis for less than 1 year and whose residual urine volume was greater than 0.1 litre per day. During one single session of dialysis, using cuprophane membranes, beta 2m increased acutely at 15 min and had risen by 32.4% at the end of the dialysis session, more than could be explained by haemoconcentration. In contrast, beta 2m acutely decreased by 38.7% during a single session using polysulphone membranes and the steady state predialysis values were lower by 37.1% after two weeks intermittent haemodialysis with polysulphone membranes. After re-exposure to cuprophane serum beta 2m increased to the original value. It is concluded that beta 2m concentrations on dialysis are a function of residual urinary volume, sex, and type of membrane used. Data are consistent with effective removal of beta 2m by membranes with high cut-off.