25-hydroxy Vitamin D Levels in Pediatric Asthma Patients and its Link with Asthma Severity.

Aim Although the relationship between 25-hydroxy (25-OH) vitamin D and asthma is known, it is unknown if 25-OH vitamin D levels are correlated with asthma severity in pediatric patients. The aim of this study was to compare the blood 25-OH vitamin D levels of asthma patients and healthy control groups and to evaluate any correlation between asthma severity and blood 25-OH vitamin D levels in pediatric asthma patients. Methods This is a cross-sectional study which shows the 25-OH vitamin D levels of asthma patients and compared to healthy controls followed by a tertiary pediatric clinic. We investigated the effect of 25-OH vitamin D levels on the severity of asthma. The severity of asthma was determined mainly by the duration of asthma diagnosis, a number of attacks in the previous year, anti-inflammatory medication usage in a previous year, atopy presence in the family, skin prick test positivity, and immunoglobulin E (IgE) levels of asthma patients. Results Compared with control groups, asthma patients had significantly lower 25-OH vitamin D, calcium (Ca) levels, and higher number of patients who had a 25-OH vitamin D deficiency, (p<0.0001, p<0.0001, p<0.0001, respectively). We found a correlation between blood 25-OH vitamin D levels and force expiratory capacity in one second (FEV1) and forced vital capacity (FVC) respectively (p< 0.001, r=0.512), (p< 0.001, r=0.513). There was an association between FEV1, FVC and blood 25-OH vitamin D levels in terms of deficient levels (<20 ng/mL) or insufficient levels (≥20 and <30 ng/mL) (p<0.001, r=0.459), (p< 0.001, r=0.450), respectively. Conclusions The 25-OH vitamin D levels were lower in pediatric asthma patients with worse spirometry results. Effects of Vitamin D supplementation need to be evaluated by well-designed studies.