Vitamin D deficiency in chronic kidney disease: Myth or reality?

Chronic kidney disease (CKD) is a public health problem, which has a prevalence of 17.2% in India. As kidney function decreases, there is a gradual deterioration in the regulation of bone mineral homeostasis. Vitamin D is recognized as the central player in the maintenance of bone health in CKD. Kidney Disease Outcomes Quality Initiative (KDOQI) guidelines suggest that vitamin D supplementation should be given to all CKD patients with serum 25-hydroxy vitaminD (25(OH)D) level < 30 ng/mL. Hence we undertook this study to evaluate the vitamin D status in South Indian patients with CKD.

Fifty-nine non-dialysis CKD patients of stage 3 and 4 were recruited and screened for 25(OH)D deficiency. Circulating levels of 25(OH)D were measured using chemiluminescence immunoassay. The estimated glomerular filtration rate (eGFR) was calculated using the Chronic Kidney Disease Epidemiology (CKD-EPI) equation. Serum calcium, phosphorous, creatinine and alkaline phosphatase levels were measured spectrophotometrically by an autoanalyzer.

Contrary to published literature, 75% of South Indian CKD patients had normal 25(OH)D (≥30 ng/mL), 15% of them had insufficient (20-29 ng/mL) and 10% had 25(OH)D deficiency (<20 ng/mL). Alkaline phosphatase levels were found to be increased in only 20% of cases. Calcium1 levels were normal in all CKD cases and hyperphosphatemia was observed in 5% of CKD patients.

We found that most of our CKD patients (75%) had normal vitamin D levels. This paradoxical finding could be explained by the fact that most of them gave a history of intake of vitamin D and calcium supplements, as advised by their doctors before coming to our institute. Hence we conclude that before prescribing vitamin D or calcium supplements to CKD patients, their 25(OH)D status should be ascertained to prevent hypervitaminosis D and its complications.