Increasing Vitamin D Serum Levels Is Associated with Reduced Pulmonary Exacerbations in Patients with Cystic Fibrosis.

Context: In 2012, The North American Cystic Fibrosis Foundation (NACFF) published new guidelines for the treatment of vitamin D deficiency in individuals with cystic fibrosis (CF). Objective: The objectives of our study were to assess the efficacy of these guidelines, and to test the effect of increasing vitamin D dosage on pulmonary function and exacerbations. Design: Pulmonary function tests and serum concentrations of 25-hydroxyvitamin D [25(OH)D] were measured 1 year before increasing vitamin D dosage according to the guidelines and at least 1 year later. In addition, days of hospitalization and pulmonary exacerbations were counted and an average per year (average number of days of hospitalization and average number of pulmonary exacerbations [PEA], respectively) was calculated. Setting and Participants: A total of 90 patients from The Cystic Fibrosis Clinic at Hadassah Mount-Scopus Hospital, Jerusalem, Israel. Results: The mean serum concentration of vitamin D increased significantly from 20.97 ng/mL (52.34 nmol/L) at baseline to 25.41 ng/mL (63.42 nmol/L) at the end of follow-up (P < 0.001). The number of PEA decreased significantly from 2.79 +/- 3.96 to 2.15 +/- 2.91 (P = 0.007). The change in vitamin D levels was correlated with a decrease in PEA (correlation coefficient = -0.318, P = 0.002). Conclusions: The NACFF guidelines for management of vitamin D deficiency improve vitamin D levels in patients with CF but did not reach the normal values in most patients. The increase in vitamin D serum levels was, however, associated with a decrease in number of pulmonary exacerbations.