Background Accurate prediction of prognosis in idiopathic membranous nephropathy (iMN) allows restriction of immunosuppressive therapy to patients at high risk for ESRD. Here we re-evaluate urinary lowmolecular- weight proteins as prognostic markers and explore causes of misclassification. Design, setting, participants, & measurements In a cohort of 129 patients with serum creatinine concentration <135 μmol/L and proteinuria ≥3.0 g/10 mmol, urinary α1- (uα1m) and β2-microglobulin (uβ2m) excretion rate was determined. Urinary α1m and uβ2m-creatinine ratio was also obtained. We defined progression as a rise in serum creatinine ≥50% or ≥25% and an absolute level ≥135 μmol/L. Results Median survival time was 25 months, and 47% of patients showed progression. The area under the receiver operating characteristic curve for uβ2m was 0.81 (95% CI: 0.73 to 0.89). Using a threshold value of 1.0 μg/min, sensitivity and specificity were 73% and 75%, respectively. Similar accuracy was observed for the uβ2m-creatinine ratio with sensitivity and specificity of 75% and 73%, respectively, at a threshold of 1.0 μg/10 mmol creatinine. Similar accuracy was found for uα1m and uα1m-creatinine ratio. Blood Pressure and cholesterol contributed to misclassification. Repeated measurements improved accuracy in patients with persistent proteinuria: the positive predictive value of uβ2m increased from 72% to 89% and the negative predictive value from 76% to 100%. Conclusions Urinary excretion of uβ2m and uβ2m predict prognosis in iMN. A spot urine sample can be used instead of a timed sample. A repeated measurement after 6 to 12 months increases prognostic accuracy. © 2011 by the American Society of Nephrology.
CITATION STYLE
van den Brand, J. A. J. G., Hofstra, J. M., & Wetzels, J. F. M. (2011). Low-molecular-weight proteins as prognostic markers in idiopathic membranous nephropathy. Clinical Journal of the American Society of Nephrology, 6(12), 2846–2853. https://doi.org/10.2215/CJN.04020411
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