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