Clinical and demographic predictors for vitamin D deficiency in multiethnic Asian patients with chronic kidney disease

BACKGROUND: Vitamin D deficiency is common in patients with chronic kidney disease (CKD) and can cause skeletal and extraskeletal complications. The purpose of this study is to determine the clinical and demographic risk factors for vitamin D deficiency in multiethnic CKD patients in Singapore, a sun-rich country, so that patients at risk can be identified and treated early. METHODS: Pre-dialysis CKD patients from the National University Hospital (NUH), Singapore, Outpatient Renal Clinic who had their serum 25-hydroxyvitamin D [25(OH)D] levels measured between January 2008 and October 2010 were included. Their clinical and demographic parameters were collected from hospital databases and medical charts. Logistic regression was used to identify potential predictors for vitamin D deficiency in these patients. Two models, M(t30) and M(t16,) were built using threshold serum 25(OH)D levels of ≤30 and <16 ng/mL, respectively. RESULTS: Of the 219 patients included, 82.7 and 25.6% had serum 25(OH)D levels ≤30 and <16 ng/mL, respectively. Predictors identified for vitamin D deficiency include absence of vitamin D supplementation, type 2 diabetes mellitus (DM), non-cancer diagnosis, younger age, Malay race, treatment with calcitriol and higher serum bicarbonate (CO(2)) levels. Common predictors for the two models were lack of vitamin D supplementation and DM. The areas under the receiver-operating characteristic (ROC) curve for the validation sets were 0.697 and 0.687 for the M(t30) and M(t16) models, respectively. CONCLUSIONS: Vitamin D deficiency is common among multiethnic CKD patients in Singapore. Risk factors identified in this study include absence of vitamin D supplementation, DM, non-cancer diagnosis, young age, Malay race, calcitriol treatment and higher serum CO(2). The knowledge of these risk factors is useful for predicting vitamin D deficiency in CKD patients in Singapore.