Bioavailable vitamin D levels in children with first episode nephrotic syndrome: A longitudinal study.

Abstract

Abstract Background Bioavailable vitamin D levels is could be a better marker than total 25 hydroxy vitamin D levels to assess vitamin D status in children with nephrotic syndrome. Primary objective To assess the levels of Serum bioavailable vitamin D in children aged 1 to 12 years with idiopathic FENS and in healthy controls. Secondary objective 1. To measure the levels of bioavailable vitamin D in FENS and after 4 weeks of standard steroid therapy induced remission. 2. To compare levels of serum and urine VDBP in FENS and after 4 weeks of standard steroid therapy induced remission. Materials and Methods A longitudinal study was conducted in children between age 1 to 12 years with idiopathic first episode nephrotic syndrome. After diagnosis of nephrotic syndrome as per ISPN guidelines, additional investigations like calcium, phosphorus, ALP, 25 hydroxy vitamin D, PTH, serum Vitamin D binding protein (VDBP) and urinary VDBP. Bioavailable and free vitamin D was calculated using above data. The patients were followed up after 4 weeks of remission and investigations were repeated and bioavailable vitamin D was calculated again, later results were compared and analysed. Appropriate statistical tests were applied for parametric and non-parametric data. P value of less than 0.05 was considered statistically significant. Results: The mean 25 hydroxy vitamin D level was 11.27(6.08) at FENS and at 4 weeks follow-up it was 13.65 (6.24). Hence children with FENS remained deficient in 25 hydroxy vitamin D, both during relapse and remission compared to healthy controls (15.97 ng/ml). The mean serum VDBP level in FENS during relapse was 242.90 (127.75). There was significant correlation of serum VDBP with serum albumin levels (p value 0.04). At 4 weeks of remission the VDBP levels increased to 550.7(219.7), this increase was significant (p value <0.001). The mean free vitamin D at FENS was 1.54 (1.70) pg/ml, on follow-up visit at 4 weeks of remission the free vitamin D levels decreased to 0.68 (0.53) pg/ml. The mean bioavailable vitamin D in FENS during relapse was 0.75 (0.84) ng/ml and on follow-up at 4 weeks of remission increased to 1.11 (0.84) ng/ml (p value = 0.015). Conclusion Children with FENS are deficient of vitamin D levels. The free and bioavailable vitamin D levels are reduced in children with FENS during proteinuria, as compared to healthy controls. Further studies showing correlation of bioavailable vitamin D and 25 hydroxyvitamin D with bone mineral density are required in children to validate the usage of bioavailable vitamin D in clinical practice.