High peritoneal clearance of small molecules did not provide low serum β2-microglobulin concentrations in peritoneal dialysis patients

Abstract

◆ Objective: Although early reports demonstrated that serum β2-Microglobulin (s-β2m) concentrations in patients on peritoneal dialysis (PD) were lower than those in patients on hemodialysis (HD), more recent studies demonstrated lower S-β2m concentrations in HD patients treated mainly with high-flux synthetic membranes. We therefore compared s-β2m concentrations between patients on PD and on HD, and also analyzed the relationship between s-β2m concentrations and other parameters in patients on PD. ◆ Patients and Methods: We investigated 24 patients who had been undergoing PD [11 on continuous ambulatory peritoneal dialysis, 13 on continuous cycling peritoneal dialysis] for 4.3 ± 2.7 years, and 24 patients who had been undergoing HD with high-flux synthetic membranes for 6.1: ± 3.2 years. Concentrations of s-β2m in the PD patients were compared to concentrations in the HD patients. In patients on PD, we also analyzed the relationship between s-β2m concentration and other parameters, including residual renal function, total weekly Kt/V urea, total weekly creatinine clearance (CCr), and dialysis schedules. ◆ Results: We found no significant difference in s-β2m concentrations between the PD and HD patients (33.6 ± 10.4 mg/L vs 30.3 ± 10.5 mg/L respectively). Concentrations of s-β2m in PD patients rose with PD duration and were significantly inversely correlated with residual renal function (r = -0.71, p < 0.0001). Unexpectedly, concentrations of s-β2m in anuric PD patients rose as peritoneal CCr increased. And most of the patients with high s-β2m levels fell into the high or high-average transport categories according to a peritoneal equilibration test. ◆ Conclusions: Concentrations of s-β2m in patients on PD did not differ significantly from concentrations in HD patients who were using high-flux synthetic membranes. The contribution of residual renal function to removal of β2m was more important than the contribution of peritoneal clearance. High peritoneal clearance of small molecules did not result in low s-β2m concentrations, especially in anuric patients with accelerated peritoneal permeability.