Diagnostic value of soluble urokinase receptor serum levels in adults with idiopathic nephrotic syndrome

Introduction: Recent studies suggest that soluble urokinase receptor (suPAR) levels could be useful for distinguishing idiopathic focal segmental glomerulosclerosis (FSGS) from other glomerulopathies that cause nephrotic syndrome, but these data have not been confirmed in independent studies. The objective of our study is to analyse whether circulating levels of suPAR are useful for identifying primary kidney disease in patients affected with nephrotic syndrome secondary to FSGS, minimal change disease or idiopathic membranous nephropathy. Methods: We measured circulating suPAR at diagnosis in 60 patients with nephrotic syndrome secondary to FSGS, minimal change disease (MCD) and membranous nephropathy (MN). The correlations between suPAR levels and demographic, clinical and biochemical variables were analysed. The sensitivity and specificity of suPAR in distinguishing FSGS patients were analysed by ROC curves. Results: After adjusting for age and renal function, suPAR levels were significantly higher in patients with FSGS than in those with MCD (P<.001), but there were no differences between FSGS and MN (P=.12). A suPAR value >3452pg/ml had a sensitivity of 73.7% and a specificity of 72.5%, with an area below curve (ABC) of 0.782±0.124, P=.001, for identifying patients with FSGS. After excluding patients with MN, a value >3531pg/ml had a specificity of 99.93% for distinguishing between MCD and FSGS. Conclusions: suPAR values alone do not distinguish between the three types of glomerulopathy. Nevertheless, after excluding the diagnosis of MN, a suPAR level >3531pg/ ml could have a high specificity (but a low sensitivity) in the diagnosis of FSGS.