Expression of urinary neutrophil gelatinase-associated lipocalin and its clinical significance in children with idiopathic nephrotic syndrome

Abstract:

OBJECTIVE: To investigate the urinary neutrophil gelatinase-associated lipocalin (NGAL) concentration in children with idiopathic nephrotic syndrome (INS) and its clinical significance. METHODS: Thirty-four children newly diagnosed with INS received oral prednisone for 4 weeks. Patients whose urinary protein did not become negative were classified as steroid-resistant nephrotic syndrome (SRNS) group, while those whose urinary protein did become negative were classified as steroid-sensitive nephrotic syndrome (SSNS) group. Morning midstream urine specimens were collected from all patients before use of prednisone and after 1, 2, 3, and 4 weeks of treatment with prednisone. Enzyme-linked immunosorbent assay was used to measure the urinary NGAL concentration. Meanwhile, urinary creatinine (Cr) concentration was measured, and urinary NGAL concentration in a single urine collection was adjusted according to the urinary Cr excretion. The two groups were compared in terms of urinary NGAL/Cr ratio. RESULTS: Compared with the SRNS group, the SSNS group had significantly decreased urinary NGAL/Cr ratios after 3 and 4 weeks of prednisone treatment (P<0.05). Compared with the SRNS group, the SSNS group had a significantly decreased urinary β2-MG/Cr ratio after 4 weeks of prednisone treatment (P<0.05). In both groups, urinary NGAL/Cr ratio was positively correlated with urinary protein/Cr ratio (r=0.510, P<0.01). The results of ROC curve analysis showed when diagnostic cut-off point of urinary NGAL/Cr was 0.043 by 3 weeks after treatment, sensitivity and specificity achieved 100% and 79.2% respectively. CONCLUSIONS: Urinary NGAL/Cr ratio remains high in children with SRNS, while this ratio decreases gradually during prednisone treatment in children with SSNS, and it falls ahead of urinary β2-MG/Cr ratio. These results suggest that dynamic monitoring of urinary NGAL/Cr ratio is useful for early judgment of response to prednisone in patients with INS.