Beta-2-microglobulin is superior to N-acetyl-beta-glucosaminidase in predicting prognosis in idiopathic membranous nephropathy

Abstract

Background: An accurate prediction of prognosis in patients with idiopathic membranous nephropathy (iMN) would allow restriction of immunosuppressive treatment to patients who are at highest risk for end-stage renal disease (ESRD). Several markers of proximal tubular cell injury have been used as predictors of prognosis. In this study we compared the accuracy of urinary beta-2-microglobulin (Uβ2m) and N -acetyl-beta-glucosaminidase (Uβ-NAG) in predicting renal insufficiency and remission rates. Methods: Fifty-seven patients with iMN (38 M, 19 F; age 48 ± 16 years), a nephrotic syndrome and a serum creatinine level 50%. Remission was defined as a proteinuria Results: The mean follow-up was 80 ± 36 months. The mean serum creatinine concentration was 89 ± 20 μmol/l, serum albumin 24 ± 5.3 g/l and proteinuria 8.9 ± 4.8 g/24 h. Thus far, 28 (49%) patients have reached the predefined end point of renal failure. Multivariate analysis identified Uβ2m as the strongest independent predictor for the development of renal insufficiency. Sensitivity and specificity were 81 and 90% respectively for Uβ2m (threshold value 54 μg/mmol cr), and 74 and 81% respectively for Uβ-NAG (threshold value 2.64 U/mmol cr). The overall remission rate was 44%. A remission occurred in 78% of patients with low Uβ2m and in 14% of patients with high Uβ2m, and respectively in 71% of patients with low Uβ-NAG and 21% of patients with high Uβ-NAG. Conclusions: Although both Uβ2m and Uβ-NAG predicted progression and remission in iMN, Uβ2m was more accurate. High specificity in predicting prognosis should be pursued to avoid unnecessary immunosuppressive therapy. We therefore conclude that Uβ2m is superior to Uβ-NAG in predicting prognosis in patients with iMN.