Definitions
Asthma is defined as a history of respiratory symptoms, such as
wheezing, shortness of breath, chest tightness, and cough, that vary
over time and in intensity, together with variable expiratory airflow
limitation. Patients with characteristic asthma symptoms were diagnosed
by means of spirometry and reversibility testing in accordance with the
Global Initiative for Asthma (GINA) guideline. Patients younger than
five were diagnosed on the basis of symptoms and inhaled corticosteroid
responsiveness. All the patients had been under control with step 2-4
treatment for at least three months.20
Allergic rhinitis was defined as symptoms of nasal itching, congestion,
rhinorrhea, and sneezing according to Allergic Rhinitis and its Impact
on Asthma (ARIA) guidelines. The condition was classified as
intermittent or persistent depending on duration and as mild or moderate
to severe according to severity.21
Skin prick test
Skin prick tests were performed using a prick test applicator (MedBlue
One) on the flexural aspect of the forearm in line with standard
guidelines, using standardized glycerinated extracts from LOFARMA
(Milan, Italy) (1% weight/volume). Cat sensitization was defined as
positive in children with a skin prick test induration diameter ≥3mm for
cat epithelium solution.22 Detailed information about
skin prick testing was given in supplementary data.
Exclusion criteria
The exclusion criteria for the study group were a history of chronic
lung disease (except for asthma), first- and secondhand smoking
exposure, chronic cardiac and neuromuscular disease, a history of low
birth weight/premature birth/neonatal mechanical ventilation,
malnutrition, obesity, malignancy, immune deficiencies, connective
tissue disease, acute or chronic respiratory disease (adenoid
hypertrophy or chronic sinusitis etc.) in the previous four weeks, or
history of hospitalization or admission to intensive care unit in the
previous year. Patients using inhaled short-acting beta agonists,
systemic steroids, anticholinergics, and decongestants were also
excluded from the study.
Exclusion criteria for the HC group were the presence of allergic
respiratory diseases such as asthma and allergic rhinitis in addition to
the criteria listed above.
Study design
When patients with asthma and/or allergic rhinitis presented to the
pediatric allergy outpatient clinic for skin prick testing, those with
cat sensitization were invited to take part in the study. Routine
physical examinations were performed, and anthropometric measurements
were recorded on the patients who agreed to participate in the study.
Routine endoscopic authorhinolaryngological examinations were performed
in the Ear-nose-throat (ENT) clinic in order to exclude any allergic
rhinitis complications and/or comorbidities such adenoid hypertrophy or
acute/chronic sinusitis. The patients were then referred to the
respiratory function tests laboratory for IOS and spirometry.
Age- and sex-matched healthy subjects who had presented for routine
health checks were randomly recruited from the general pediatric
outpatient clinic and invited to participate in the study. Routine
physical examinations were conducted, anthropometric measurements were
recorded, and these were then referred to the respiratory function test
laboratory.