Study design, setting and participants
Children aged 6 to 17 with physician-diagnosed asthma who were regularly followed up in the Pediatric Allergy and Asthma Unit of Gulhane School of Medicine between 2014 and 2017 were enrolled in the study along with age and sex-matched control subjects without any physician diagnosed asthma who admitted to outpatient department of our unit for routine medical checkup. They had no history of wheezing or infection during the last 4 weeks before the study enrollment.
Asthma was defined as current symptoms (wheeze and cough) and positive bronchodilator responsiveness (improvement of FEV1 by 12% or more following administration of 200 mcg salbutamol), and/or a positive response to a trial of therapy with inhaled or oral corticosteroids (3). Asthma severity is assessed retrospectively from the level of treatment required to control symptoms and exacerbations in the last year according to GINA guidelines. “Mild asthma” is asthma that is well controlled with Step 1 or Step 2 treatment, “moderate asthma” is asthma that is well controlled with Step 3 treatment and “severe asthma” is asthma that requires Step 4 or 5 treatment. Asthma control status of the patients were also evaluated according to GINA guidelines (3). Patients with an acute exacerbation of asthma requiring systemic corticosteroids during the previous 3 months and other known systemic disorders were excluded.
The study was approved by the institutional review board of Gulhane School of Medicine and written informed consent was obtained from parents.
Study measurements