Beta-2 Microglobulin in Peritoneal Dialysis Patients: Serum Levels and Peritoneal Clearances

Beta-2 microglobulin (B2M) is amyloidogenic in long-term hemodialysis patients, with amyloid deposition manifesting as lytic bone lesions, carpal tunnel syndrome, destructive arthropathies, tenosynovitis, and pathologic fractures. To study the behavior of this protein in the peritoneal dialysis population, serum levels of B2M from 14 chronic peritoneal dialysis (CPD) patients (4IPD, 10 CAPD) were compared to those of 15 chronic hemodialysis patients, and peritoneal clearances were measured in 9 CAPD patients. Standard cuprophan dialyzers were used for hemodialysis. Serum B2M levels were significantly lower in the peritoneal dialysis group (mean ± SD 73.2 ± 20.9 mg/L) than in the hemodialysis group (100.3 ± 24.7 mg/L, p < .004). When CAPD patients alone were compared to the hemodialysis patients, lower serum B2M levels were again apparent, with mean 68.7 ± 16.4 mg/L (p ≤ .002). Mean serum B2M in IPD patients (84.6 ± 28.9 mg/L) did not differ statistically from either the CAPD or the hemodialysis group. Peritoneal clearance of B2M, urea nitrogen, and creatinine over a 6 h exchange were obtained in 9 CAPD patients without peritonitis. Mean clearance (±SD) of B2M was 0.9 ± 0.4 ml/min/1.73 m2, urea nitrogen 5.3 ± 0.3 ml/min/1.73 m2, and creatinine 4.2 ± 0.8 ml/min/1.73 m2. Mean loss of B2M via the peritoneal cavity was 19.9 ± 6.6 mg/2 L-exchange/1.73 m2 (range 7.7 to 26.2 mg/2 L-exchange/1.73 m2). Decreased serum B2M in peritoneal dialysis patients is consistent with increased clearance by the peritoneal membrane versus standard cellulosic hemodialysis membranes. Whether use of CPD rather than hemodialysis can prevent or even treat dialysis-associated amyloidosis (AB2M) remains speculative.