Vitamin D status of children with moderate to severe chronic Kidney Disease at a Tertiary Pediatric Center in Cape Town

Abstract

The prevalence of suboptimal Vitamin D levels is higher in patients with chronic kidney disease (CKD) than in the general population. Recent findings suggest that progression of CKD is linked to a suboptimal Vitamin D level. A high percentage of CKD patients have severe Vitamin D deficiency. These patients also have a low level of 25-hydroxy-vitamin D [25(OH)D] and consequently, a reduced ability to form active 1,25-dihydroxyvitamin D. Various factors underlie the low level of 25(OH)D, including a sedentary lifestyle, decreased intake of Vitamin D due to CKD-related dietary restrictions, and decreased synthesis of Vitamin D in skin due to uremia. All these factors may be particularly influential in patients with progressively worsening CKD, including those receiving chronic dialysis. The objective of our study is to determine the prevalence of Vitamin D deficiency in children with CKD stages three to five and those receiving chronic dialysis, to ascertain whether there is a relationship between Vitamin D deficiency and the stage of CKD, and to identify any clinical correlates associated with the Vitamin D status. A single-center, retrospective review was conducted of 46 children (younger than 18 years) with CKD stages 3–5D who attended the renal clinic of the Red Cross Children’s Hospital between October 2013 and November 2014. In total, 73.9% of the study population had suboptimal Vitamin D levels (43.5% and 30.4% had Vitamin D deficiency and insufficiency, respectively). The prevalence of Vitamin D deficiency was significantly higher in older children (≥10 years of age) than in younger children (P = 0.000) but did not significantly differ between males and females (P = 0.693). In total, 12 of 15 black children (80%), 19 of 26 colored children (73.1%), two of four white children (50%), and one Asian child (100%) had suboptimal Vitamin D levels. Neither white nor Asian child had Vitamin D deficiency. In addition, 90% of patients undergoing chronic dialysis, 80% of whom were receiving peritoneal dialysis, had suboptimal Vitamin D levels. Age, weight, height, and the albumin concentration were significantly associated with the Vitamin D level. There was a positive linear relationship between the Vitamin D level and the serum albumin concentration (Spearman’s rho correlation coefficient = 0.397, P = 0.007). In total, 87.5% of patients with nephrotic-range proteinuria had suboptimal Vitamin D levels, and 80% were Vitamin D deficient (P = 0.004). A higher percentage of Vitamin D deficiency/insufficiency cases was documented during the winter (24/34, 70.6%) than during the summer (10/34, 29.4%); however, this difference was not statistically significant (P = 0.685). Sub-optimal Vitamin D is high among children with moderate to severe CKD and significantly higher in those undergoing chronic dialysis. The emerging evidence of the role of Vitamin D in slowing progression of CKD highlights the need for monitoring and correction of Vitamin D levels in predialysis children.