The Potential of Vitamin-D-Binding Protein as a Urinary Biomarker to Distinguish Steroid-Resistant from Steroid-Sensitive Idiopathic Nephrotic Syndrome in Iraqi Children

Objective: To determine the ability of uVDBP to discern SRNS from steroid-sensitive nephrotic syndrome (SSNS) in Iraqi children. Materials and Methods: This cross-sectional study enrolled children with SRNS (n=31) and SSNS (n=32) from the pediatric nephrology clinic of Babylon Hospital for Maternity and Pediatrics over three months. Patients' characteristics in terms of demographics, clinical data, and urinary investigations were collected. Quantitative analysis of uVDBP levels was undertaken via a commercially available ELISA kit. Results: The median uVDBP values were significantly higher (p-value<0.001) in the SRNS group (median=10.26, IQR=5.91 μg/mL) than in the SSNS group (median=0.953, IQR=4.12 μg/mL). A negative correlation was noted between uVDBP levels and estimated glomerular filtration rate (eGFR) (Spearman's rho coefficient= − 0.494, p=0.001). Nevertheless, the rise in uVDBP concentrations was still considerable in children with SRNS whose eGFR measurements were above 60 mL/min/1.73 m2. The study revealed a good discriminatory power for uVDBP as a predicting parameter to distinguish SRNS from SSNS (AUC= 0.909, p<0.0001. The optimal uVDBP cut-off value of 5.781 μg/mL was associated with a sensitivity of 0.839 and specificity of 0.844 to differentiate SRNS from SSNS. Conclusion: Considering its significant discriminatory strength, uVDBP can be considered as a potential marker to noninvasively distinguish children with SRNS from those with SSNS.