Association of Urinary Vitamin D Binding Protein and Neutrophil Gelatinase-Associated Lipocalin with Steroid Responsiveness in Idiopathic Nephrotic Syndrome of Childhood

Abstract

Idiopathic nephrotic syndrome (NS) is one of the most common kidney diseases of childhood. In this study, we assessed urine Vitamin-D binding protein (VDBP) and neutrophil gelatinase-associated lipocalin (NGAL) levels as a predictor of steroid responsiveness in idiopathic NS. This cross-sectional study included children with steroid-resistant NS (SRNS) (n = 28), steroid-sensitive NS (SSNS) (n = 28), and healthy controls (n = 28). Urine levels of VDBP and NGAL were measured using a commercially available ELISA kit and normalized to urine creatinine (Cr). Urine microalbumin (MALB) was measured using nephelometer, and MALB/Cr was calculated. Urine Vitamin-D binding protein (uVDBP) and urine neutrophil gelatinase-associated lipocalin (uNGAL) levels were statistically significantly higher (P < 0.001) in patients with SRNS (701.12 ± 371.64 ng/mL and 28.42 ± 15.40 ng/mL, respectively) than in patients with SSNS (252.87 ± 66.34 ng/mL and 8.86 ± 5.54 ng/mL, respectively) and normal controls (34.74 ± 14.10 ng/mL and 6.79 ± 1.32 ng/mL, respectively). Estimated glomerular filtration rate shows a significant negative correlation with MALB/Cr, uVDBP, and uNGAL. However, uVDBP and uNGAL showed a much higher discriminatory ability for differentiating SRNS from MALB/Cr. uVDBP and uNGAL at the cutoff value of 303.81 and 13.1 ng/mL, respectively, yielded the optimal sensitivity (82% and 86%) and specificity (78% and 89%) to distinguish SRNS from SSNS. Urine levels of VDBP and NGAL can predict steroid responsiveness in patients with idiopathic NS.