Vitamin D deficiency in pediatric patients with cystic fibrosis: associated risk factors in the northern United States.

Abstract Cystic fibrosis (CF) is associated with vitamin D deficiency, which can lead to adverse effects including recurrent pulmonary infections and osteoporosis. We longitudinally investigated calcifediol or 25-hydroxyvitamin D (25(OH)D) levels for our pediatric patients with CF based on the time of year as well as vitamin D supplementation dosing ranges for these patients at our CF center. We retrospectively evaluated vitamin D deficiency in our pediatric CF center for 2 years (baseline and annually) while evaluating 25(OH)D serum changes based on vitamin D supplementation, seasonality, patient age, and other factors associated with CF. Vitamin D supplementation was noted to be higher than current Cystic Fibrosis Foundation dosing recommendations, and no patient experienced vitamin D toxicity. Seasonality was a strong indicator of 25(OH)D levels, especially during summer or fall. Significantly fewer patients with initially low 25(OH)D levels maintained low levels at the conclusion of the study, suggesting benefit. Older patient age and higher supplemental dosing correlated with significantly lower 25(OH)D levels. This study suggests that targeted intervention among pediatric patients with CF living in northern latitudes of the United States, especially older children, is needed to prevent vitamin D deficiency.