The vitamin D insufficiency and deficiency are widely prevalent in Korean children with predialysis CKD. The prevalence of serum 25 (OH)D less than 30 ng/mL was 77.8% in pediatric patients with predialysis CKD. Recent data showed that only 2.9% was vitamin D sufficient in Korean children and its prevalence increases in winterspring season, in overweight children and in older age groups. In Korean children with dialysis in the same unit, vitamin D deficiency and insufficiency were found in 83.0%.
Pediatric patients with chronic dialysis in our unit showed mean 25(OH)D levels of below 20 ng/mL, and our predialysis CKD patients above 20 ng/mL. These finding is compatible with the previous results that vitamin D deficiency was more severe in dialysis patients than in early CKD patients. The recent studies and our findings suggested that vitamin D deficiency is strongly associated with the more advanced stage of CKD.
Several explanations were possible. First, the pediatric patients with more advanced stage of CKD might be under the condition of more restricted diet and physical activity, and vitamin D deficiency is more common. Second, the patients with advanced CKD and overt proteinuria might have greater loss of urinary vitamin D metabolites which can influence on inadequate vitamin D status such as vitamin D binding protein.