Serum β₂ microglobulin (β₂MG) level is a potential predictor for encapsulating peritoneal sclerosis (EPS) in peritoneal dialysis patients

Background: Encapsulating peritoneal sclerosis (EPS) is a serious complication in patients undergoing continuous ambulatory peritoneal dialysis (CAPD) or automated peritoneal dialysis (APD). The aim of this study was to find a predictor for EPS. Methods: Patients with EPS who were detected by a historical cohort study using clinical data of 219 CAPD patients at our hospital. We recruited 25 patients with EPS who were compared with the patients without EPS who were matched for age and dialysis period as controls. Differences between the two groups (non-EPS group and EPS group) with respect to age, gender, primary disease, dialysis period, serum urea nitrogen, serum creatinine, β₂MG, CRP and PET (peritoneal equilibration test) category (determined by the peritoneal function testing) were analyzed. Results: According to multiple regression analysis, a high β ₂MG level was an independent risk factor for EPS (odds ratio 1.162, 95% confidence interval 1.026 - 1.317, p = 0.018). Other clinical markers did not show positive significance. A ROC (receiver operating characteristic) curve was prepared to evaluate the suitability of β₂MG measurement as a screening test. The sensitivity was 64% and the specificity was 80% when a β₂MG level of 37.0 mg/dl was taken as the cut-off value. The odds ratio for occurrence of EPS was 8.8 when β₂MG level was in the range of 35 -40 mg/dl, 13.5 when β₂MG level was > 40 mg/dl and 1 when β₂MG level was < 30 mg/dl. Conclusion: These findings suggest that β₂MG is useful as a screening test for the onset of EPS, and that β₂MG and accumulation of middle-molecular uremic substances may be related to the pathophysiology of EPS.