Bronchial reactivity, inflammatory and allergic parameters, and vitamin D levels in children with asthma

BACKGROUND: A low serum vitamin D level may represent amarker of other perplexing factors that may lead to increased asthma prevalence and severity. Our aim was to assess the correlation between vitamin D levels and asthma and allergy markers in a subgroup of children with fewer confounding factors. METHODS: Non-obese children (6–18 y old) with asthma who were not receiving anti-inflammatory treatment were recruited. Subjects underwent spirometry with a methacholine challenge test, and fractional exhaled nitric oxide (F_ENO), serum vitamin D levels, total immunoglobulin E (IgE) levels, blood eosinophil counts, and high-sensitivity C-reactive protein levels were determined. The primary end point was the correlation between vitamin D level and airway hyper-responsiveness as assessed by a methacholine challenge test. The secondary end point was the correlation between vitamin D level and F_ENO, systemic inflammatory markers, and allergy. RESULTS: Seventy-one children with asthma (25 females, 35%; 12.5 ± 3.6 y of age) were included. The median vitamin D level was 23 ng/mL (range of 6–48.5, mean of 23.02 ± 7.74), the median IgE level was 305 IU/mL (range of 4.3–4,240), the median provocational concentration of methacholine that produced a 20% decrease in FEV₁ was 1.1 mg/mL (range of 0–13.9), and the median F_ENO was 26.5 ppb (range of 3.6–285). No correlation was found between vitamin D level and response to the methacholine challenge test, F_ENO, high-sensitivity C-reactive protein levels, IgE levels, eosinophil counts, and frequency of allergic rhinitis or atopic dermatitis. CONCLUSIONS: In our group of children with asthma, no correlation was found between the level of vitamin D and the degree of airway reactivity, airway inflammation, and allergy. The cause-and-effect relationship between vitamin D, asthma, and allergy should be further clarified. (ClinicalTrials. gov registration NCT01287455).