High urinary excretion of kidney injury molecule-1 is an independent predictor of end-stage renal disease in patients with IgA nephropathy

Abstract

Background. The variable course of immunoglobulin A nephropathy (IgAN) warrants accurate tools for the prediction of progression. Urinary kidney injury molecule-1 (KIM-1) and neutrophil gelatinase-associated lipocalin (NGAL) are markers for the detection of early tubular damage caused by various renal conditions. We evaluated the prognostic value of these markers in patients with IgAN.Methods. We included patients (n = 65, 72% male, age 43 ± 13 years) with biopsy-proven IgAN, who were evaluated for proteinuria. Urinary KIM-1 and NGAL were measured by enzyme-linked immunosorbent assay. We analysed data using Cox regression for the outcome end-stage renal disease (ESRD).Results. Median serum creatinine was 142 μmol/L and proteinuria 2.2 g/day. During follow-up (median 75 months), 23 patients (35%) developed ESRD. In patients with IgAN median urinary KIM-1 excretion was 1.7 ng/min and NGAL excretion was 47 ng/min, both significantly higher than in healthy controls. KIM-1 and NGAL were correlated with proteinuria (r = 0.40 and 0.34, respectively, P < 0.01) and each other (r = 0.53, P < 0.01) but not with estimated glomerular filtration rate (eGFR). Interestingly, KIM-1 was not significantly correlated with the excretion of α1-microglobulin (α1m) and β2-microglobulin (β2m), known markers of tubular injury. Univariate analysis showed that baseline serum creatinine and urinary excretion of total protein, α1m, β2m, immunoglobulin G, KIM-1 and NGAL were significantly associated with ESRD. By multivariate analysis, serum creatinine and KIM-1 excretion proved to be significant independent predictors of ESRD.Conclusion. KIM-1 and NGAL excretion are increased in patients with IgAN and correlate with proteinuria but not with eGFR. Baseline serum creatinine and urinary KIM-1, but not proteinuria, are independent predictors of ESRD. © The Author 2011. Published by Oxford University Press on behalf of ERA-EDTA. All rights reserved.