Urinary Vitamin D Binding Protein as a Biomarker to Assess Steroid Responsiveness in Childhood Idiopathic Nephrotic Syndrome

Background: Nephrotic syndrome (NS) is the most common glomerular disease in children. It is characterized by recurrent attacks of proteinuria, hypoalbuminemia, and edema. The purpose of this study was to evaluate the value of urinary vitamin D binding protein (uVDBP) as a biomarker for differentiating steroid-resistant nephrotic syndrome (SRNS) from steroid-sensitive nephrotic syndrome (SSNS). Methods: This was a prospective case-control study conducted with 40 children aged 2-17 years diagnosed with idiopathic NS in the pediatric department of Benha University Hospital. The study period was from April 2022 to March 2023. The participants were divided into three groups: Group A included 20 children with SRNS, Group B included 20 children with SSNS, and Group C included 20 healthy children as a control group. Results: uVDBP levels were significantly different across the groups: 701.5 ng/mL (±153.1) in Group A, 483.6 ng/mL (±157.8) in Group B, and 423.9 ng/mL (±171.8) in Group C, with a highly significant difference (p < 0.001). uVDBP showed a significant positive correlation with the urinary albumin creatinine ratio (p < 0.001) and a significant negative correlation with serum albumin (r=-0.411, p=0.001). An ROC curve of uVDBP was conducted to discriminate between nephrotic syndrome groups. uVDBP showed moderate accuracy (AUC=0.833) for discrimination between nephrotic syndrome groups. Conclusion: uVDBP levels were significantly different among the three groups (SRNS, SSNS, and healthy controls). Our findings suggest that uVDBP could be a potential biomarker for distinguishing between SRNS and SSNS in pediatric patients with nephrotic syndrome.