Urinary vitamin d binding protein level as a predictor of steroid resistance in nephrotic syndrome – a cross sectional study from south tamilnadu

Background: Nephrotic syndrome(NS) is characterised by massive proteinuria, hypoalbuminemia and oedema.Vitamin D binding protein (VDBP) which closely resembles albumin in its molecular weight and isoelectric point is excreted in nephrotic syndrome.At present,there are no non-invasive markers available to screen or diagnose Steroid Resistant Nephrotic Syndrome (SRNS) and biopsy still remains the gold standard method. In this study,we tested the hypothesis that urinary VDBP(uVDBP) levels are increased more in SRNS than Steroid Sensitive Nephrotic Syndrome(SSNS) Objective: To establish the association between urinary VDBP levels and steroid sensitive/resistant nephrotic syndrome. Methods: Hospital based Cross sectional study between August 2020 and June 2021.50 children aged 2 to 12 years who were newly diagnosed with nephrotic syndrome or those who presented with relapse were enrolled(study group).47 age and sex matched healthy children with normal urine analysis were also enrolled(control group). Urine was collected under strict asepticmeasures,centrifuged at 5000 rpm for 5 minutes and stored at -80°c until further analysis.uVDBP level was measured using commercially available ELISA kit (R&D Systems). Data were analyzed raw and normalized to urine creatinine. Outcome: Correlation between uVDBP, SSNS and SRNS was measured Results:uVDBP concentration was significantly higher in children with nephrotic syndrome(Mean 848ng/ml,SD 267.67ng/ml,p0.0001) than controls.Among children with nephrotic syndrome,uVDBP was significantly higher in children with Steroid Resistant Nephrotic Syndrome (Mean 1017.46ng/ml, SD 46.94ng/ml,p0.0001) than Steroid Sensitive Nephrotic Syndrome. Conclusion:uVDBP is a potential biomarker discriminating children with Steroid Resistant Nephrotic Syndrome from Steroid Sensitive Nephrotic syndrome.