Prevalence of asthmatic phenotypes and bronchial hyperresponsiveness in Turkish schoolchildren: an International Study of Asthma and Allergies in Childhood (ISAAC) phase 2 study

Abstract

Numerous epidemiologic studies have revealed that bronchial asthma affects populations without regard to frontiers. However, standardized methodological approaches are necessary to compare these populations. To investigate objective markers of childhood asthma on an epidemiologic basis and to include Turkish children in international comparisons. Parental questionnaires were collected and skin prick tests performed on fourth grade primary schoolchildren, aged 8 to 11 years, residing in Ankara, Turkey. Pulmonary function tests and bronchial challenge with hypertonic saline (HS) were conducted in children selected from this cohort with a stratified random sampling according to the presence of current wheezing. A total of 3,041 questionnaires were included in the evaluation. Skin prick tests were performed on 2,774 children (97.1%). A total of 347 children from this cohort underwent pulmonary function and bronchial challenge tests. In 18 (5.1%) of the 347 children, bronchial challenge tests could not be successfully completed. The prevalence values were 11.5% for current wheezing, 6.9% for physician-diagnosed asthma, and 7.7% for physician-diagnosed recurrent bronchitis. Population-based weighted prevalence of bronchial hyperresponsiveness (BHR) was 21.8%. Frequency of responses to HS was 38.6% among physician-diagnosed asthma cases and 30.5% among patients with current wheezing. Skin test positivity was present in 38.7% of the children with a diagnosis of asthma or asthmatic bronchitis, 35.0% of current asthmatic patients, and 19.2% of patients with current wheezing. Objective markers, in addition to the questionnaire-based prevalence figures, need to be used in epidemiologic surveys for asthma, especially in countries with inadequate health care facilities or problems with interpretation of the wheeze concept.