Relationship between plasma beta 2-microglobulin and residual diuresis in continuous ambulatory peritoneal dialysis and hemodialysis patients.

To evaluate whether the continuous ambulatory peritoneal dialysis (CAPD) technique is able per se to obtain lower beta 2-microglobulin (beta 2M) plasma levels than hemodialysis (HD) or whether other factors, such as residual diuresis, can make a significant contribution, we compared 69 CAPD and 38 cuprophan HD patients, matched for age and dialysis duration. Residual diuresis was 680.3 +/- 531.8 mL/day in CAPD and 285.5 +/- 381.8 mL/day in HD (p < 0.001) subjects. Daily diuresis was > 300 mL/day in 63.8% of CAPD and in 31.6% of HD patients. The beta 2M plasma levels were 26.3 +/- 9.9 mg/L and 34.9 +/- 13.3 mg/L (p < 0.001) in CAPD and HD, respectively. In both groups the difference was significant when we compared the patients with diuresis below versus above 300 mL/day (p < 0.001). Instead, the differences were not significant upon comparing the CAPD and HD patients with the same amount of daily diuresis. The comparison between beta 2M plasma levels and residual diuresis showed a significant inverse correlation in both groups (p < 0.001). We conclude that the dialysis technique itself does not affect beta 2M plasma levels. The diuresis volume may be a very important factor in lowering beta 2M levels in both CAPD and HD patients. CAPD's capacity to maintain a higher diuresis for longer than HD may account for the lower beta 2M plasma levels in CAPD patients.