Beta 2 microglobulin in CAPD.

The peritoneal clearance (Kp) and renal clearance (Kr) of beta 2 microglobulin (beta 2 m) were studied prospectively on 50 ESRD patients treated with CAPD, in order to determine the effect of the number of daily exchanges on Kp and to investigate the factors which influence the serum levels of beta 2m. Kr and Kp of beta 2m and creatinine (Cr) were calculated using standard formulae at the initiation of study and again at 6, 12, 18 and 24 months by collecting 24 hour urinary output and dialysate effluent. Kp of beta 2m of patients on 3 exchanges/day was .94 +/- .08 ml/min at the initiation of study and 1.1 +/- .08 at the end. For patients on 4 exchanges/day it was .99 +/- .14 ml/min and 1.1 +/- .12 respectively. There was no significant difference. Serum levels of beta 2m were lower on patients with significant residual renal function (RRF) (17 +/- .9 mg/L) than on patients without RRF (38 +/- 2 mg/L. p = .001). Serum levels of beta 2m correlated inversely with Kr of Cr and beta 2m at the initiation of study and at the end (r = .67 and .77 respectively, p = .0001). We conclude that serum levels of beta 2m correlate inversely with Kr of Cr and are expected to rise as RRF decreases. The combined peritoneal and renal excretion of beta 2m is less than its daily production. The number of dialysis exchanges does not influence Kp of beta 2m.