Predictors of Vitamin D Status in Predialysis Chronic Kidney Disease Patients: A Cross-sectional Analysis in a High Ultraviolet Climate

Abstract

Objective: To determine vitamin D status in a subtropical climate among an unselected, referred predialysis chronic kidney disease (CKD) population; assess risks and correlates; and review whether higher 25-hydroxyvitamin D (25-OHD) concentration can mitigate the decrement in circulating 1,25-dihydroxyvitamin D (1,25-OHD) normally encountered with advancing CKD. Design: Prospective cross-sectional cohort study. Setting: Renal unit in Brisbane, Australia (27°28' S). Subjects: Five hundred ninety-three consecutive CKD patients (stage 1 to 5). Main Outcome Measure: 25-OHD insufficiency (concentrations: 15 to 30 ng/mL) and deficiency (<15 ng/mL), bone-mineral parameters, including 1,25-OHD, calcium, and phosphate. Results: Despite potentially higher environmental ultraviolet (UV) exposure, only 48% of patients with CKD were 25-OHD sufficient. Traditional risks for hypovitaminosis D were maintained, and sufficiency was independently predicted by testing in the summer/autumn period (odds ratio [OR]: 2.77, 95% confidence interval [CI]: 1.88 to 4.08, P < .001), male gender (OR: 2.18, 95%CI: 1.46 to 3.24, P