title: 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 (U beta 2m) and N-acetyl-beta-glucosaminidase (U beta-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 <135 micromol/l were studied prospectively. At baseline, a standardised measurement was carried out to determine renal function and protein excretion. The end-point renal failure was defined as a serum creatinine exceeding 135 micromol/l or an increase in serum creatinine by >50%. Remission was defined as a proteinuria <2.0 g/day with stable renal function.
  
  
  RESULTS
  The mean follow-up was 80 +/- 36 months. The mean serum creatinine concentration was 89 +/- 20 micromol/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 U beta 2m as the strongest independent predictor for the development of renal insufficiency. Sensitivity and specificity were 81 and 90% respectively for U beta 2m (threshold value 54 microg/mmol cr), and 74 and 81% respectively for U beta-NAG (threshold value 2.64 U/mmol cr). The overall remission rate was 44%. A remission occurred in 78% of patients with low U beta 2m and in 14% of patients with high U beta 2m, and respectively in 71% of patients with low U beta-NAG and 21% of patients with high U beta-NAG.
  
  
  CONCLUSIONS
  Although both U beta 2m and U beta-NAG predicted progression and remission in iMN, U beta 2m was more accurate. High specificity in predicting prognosis should be pursued to avoid unnecessary immunosuppressive therapy. We therefore conclude that U beta 2m is superior to U beta-NAG in predicting prognosis in patients with iMN.
authors.affiliation: Department of Nephrology, Radboud University Nijmegen Medical Center, PO Box 9101, 6500 HB Nijmegen, The Netherlands. J.Hofstra@nier.umcn.nl
authors.forename: Julia M
authors.initials: JM
authors.lastname: Hofstra
authors.forename: Jeroen K J
authors.initials: JK
authors.lastname: Deegens
authors.forename: Hans L
authors.initials: HL
authors.lastname: Willems
authors.forename: Jack F M
authors.initials: JF
authors.lastname: Wetzels
mesh_terms: D000118:Acetylglucosaminidase / Q000652:urine*; D000328:Adult; D015415:Biomarkers / Q000652:urine; D005260:Female; D015433:Glomerulonephritis, Membranous / Q000150:complications / Q000188:drug therapy / Q000201:enzymology / Q000652:urine*; D006801:Humans; D007166:Immunosuppressive Agents / Q000627:therapeutic use; D007676:Kidney Failure, Chronic / Q000201:enzymology / Q000209:etiology / Q000652:urine; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D009404:Nephrotic Syndrome / Q000201:enzymology / Q000652:urine; D011379:Prognosis; D016016:Proportional Hazards Models; D011446:Prospective Studies; D001613:beta 2-Microglobulin / Q000652:urine*
chemical_list: D015415:Biomarkers; D007166:Immunosuppressive Agents; D001613:beta 2-Microglobulin; D000118:Acetylglucosaminidase