Abstract
BACKGROUND AND OBJECTIVES: Vitamin D deficiency (defined by serum levels of 25-hydroxyvitamin D) is common in patients with ESRD on hemodialysis, but risk factors are unknown. This study was conducted to determine whether routinely measured clinical and demographic parameters could identify dialysis patients who are vitamin D deficient. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS: Nine-hundred eight patients with 25-hydroxyvitamin D levels were identified from the Accelerated Mortality on Renal Replacement (ArMORR) cohort of incident U.S. dialysis patients and were divided into training (60%) and validation (40%) sets. Predictive models were generated from routinely assessed clinical and demographic data in the training set using logistic regression modeling, neural networks, and decision trees with vitamin D deficiency as the dependent variable. Models underwent progressive variable reduction to identify the simplest model that remained predictive. RESULTS: Seventy-nine percent of the population was vitamin D deficient (25-hydroxyvitamin D <30 ng/ml). Black race, female sex, winter season, and hypoalbuminemia (serum albumin < or =3.1 g/dl) were the strongest predictors of vitamin D deficiency. In the validation set, the presence of hypoalbuminemia and winter season increased the likelihood of vitamin D deficiency in black women (from 90% to 100%), black men (from 85% to 100%), white women (from 82% to 94%), and white men (from 66% to 92%). CONCLUSIONS: Deficiency of 25-hydroxyvitamin D is nearly universal among patients with hypoalbuminemia initiating chronic hemodialysis in winter.