Background: In epidemiological studies of asthma, questionnaires to differentiate asthmatics from non-asthmatics have proven to be cost-effective and convenient. The aim of this study was to analyze the association between hyperresponsiveness to methacholine and the validity of five items for the asthma like questionnaire recommended by the Global Initiative for Asthma (GINA).
Methods: A total of 680 subjects who visited the pulmonology department with suspected symptoms of asthma were enrolled. All participants completed five items questionnaires and underwent methacholine bronchial provocation tests (MBPT). The diagnostic value of the questionnaire was assessed through analysis of the sensitivity, specificity, and positive and negative predictive values.
Results: Multivariate logistic regression analysis showed that questionnaires about wheezing, exercise induced dyspnea and pollution-induced dyspnea were useful for differentiating asthmatics from non-asthmatics (adjusted odds ratio (OR) =2.0, 95% confidence interval (CI) 1.3-3.0; OR =2.3, 95% CI 1.5-3.5; OR =2.0, 95% CI 1.3-3.0) respectively. A total symptom score of higher than 1 was associated with the highest sensitivity (98.4%) and lowest specificity (9.4%). In contrast, a total symptom score of more than 5 was associated with the highest specificity (91.9%) and lowest sensitivity (18.5%)
Conclusions: Although questionnaires are not a sufficiently accurate method for diagnosing asthma, properly selected questionnaire can be used as effective strategies in situations such as private clinics or large population based epidemiologic studies.