Does Urinary Vitamin D-Binding Protein Have a Role in the Prediction of Steroid Resistance in Nephrotic Syndrome? A Cohort Study on Egyptian Children

Background: Nephrotic syndrome (NS) is a common glomerular disease in children, for which there are currently no noninvasive markers for predicting responsiveness to steroid treatment. Objectives: This study aimed to analyze the relationship between clinical-laboratory presentations and subsequent response to steroid therapy and to evaluate the role of urinary vitamin D binding protein (uVDBP) as a predictor of steroid resistance (SR). Methods: This was a prospective longitudinal study on 60 children with active NS (30 patients with newly diagnosed NS and 30 with relapsed NS). In addition, 30 control subjects served as a reference group for uVDBP values. The patients were evaluated before starting steroid therapy, and response to steroid therapy was monitored 4 - 8 weeks later. Results: The levels of uVDBP were elevated in patients with NS (33.33 ± 15.6 ng/mL) compared to control subjects (17.35 ± 5.5 ng/mL, P < 0.001). Also, the levels of uVDBP were significantly higher in patients with relapsed NS (37.93 ± 16.2 ng/mL) than in newly diagnosed NS patients (28.73 ± 13.67 ng/mL, P = 0.014). The level of uVDBP on presentation did not significantly differ between patients who had steroid-sensitive nephrotic syndrome (SSNS) (34.91 ± 15.01 ng/mL) and patients who had steroid-resistant nephrotic syndrome (SRNS) after 4 - 8 weeks of steroid treatment (32.60 ± 15.94 ng/mL, P = 0.417). Steroid resistance was significantly associated with a younger age of onset, specifically below 2.1 years (P = 0.023), a longer duration of the illness (P = 0.007), having more relapses (P = 0.002), total leucocytic count on presentation > 8.05 × 103/mm3 (P = 0.031), and platelet counts on presentation > 516.5 × 103/mm3 (P = 0.044). Conclusions: In this study, we found that uVDBP levels could reflect disease severity rather than predict the pattern of steroid responsiveness. Younger age of onset, longer duration of illness, previous relapses, and increased total leukocyte and platelet counts on presentation were associated with SRNS.