Role of methacholine challenge test in asthma epidemiological studies

Abstract

Since asthma-like symptoms in children are common, epidemiological studies depend on subjects’ response on surveys can overestimate true prevalence of childhood asthma. Direct bronchoprovocation tests are known to have a high sensitivity and negative predictive value for current asthma. The aim of this study was to investigate the role of methacholine challenge test in asthma epidemiological studies for estimating asthma prevalence. The subjects were 5531 elementary school children from 2009-2014 in Korea. Methacholine challenge test was performed both symptomatic and a symptomatic subjects and BHR was defined as PC 20 ≤16 mg / mL. The subject considered truly asthmatic if having BHR and a positive questionnaire response. Prevalence of asthma questions (“wheezing, ever”, “wheezing current”, “asthma diagnosis, ever” “Treatment of asthma, last 12 months” “wheezing with exercise, last 12 month”), and their association with BHR was evaluated. Comorbidities were assessed with ISAAC questionnaire, skin prick tests and pulmonary function tests. Total of 4791 children (2348 male, 2443 female) aged from 7 to 12 years were included in the analysis. The overall prevalence of BHR was 15%. Rhinitis, allergic rhinitis, allergic conjunctivitis symptoms, atopy and sensitization to Dermatophagoides pteronyssinus, Dermatophagoides farina and molds were significantly associated with BHR after adjustment to age and sex (aOR; 1.86, 1.50, 1.53, 1.94, 2.09, 1.99 and 2.05) respectively. Forced expiratory flow at 25%-75% showed slightly higher sensitivity and specificity to BHR than forced expiratory volume in 1 second. Sensitivity, specificity, and accuracy of “wheezing current”, “Treatment of asthma, last 12 months”, and “wheezing with exercise, last 12 month” were (31%, 87%, 83%), (29%, 86%, 84%), and (30%, 86%, 84%), respectively. The true asthma prevalence was 5%. The Korean version of ISAAC has low sensitivity to BHR. Both subjective and objective studies are required for accurate prediction of asthma. Regarding the technical and financial limitation, performing challenge tests to the subjects who had a positive response to any asthma question could be the best combination for estimating asthma prevalence.