Abstract
BACKGROUND: Asthma is a chronic respiratory condition affecting 3,340 cases per 100,000 individuals globally. The significant global health burden of asthma necessitates the development and use of valid diagnostic tools for epidemiological purposes. OBJECTIVE: This study evaluated the diagnostic accuracy of the International Study of Asthma and Allergies in Childhood (ISAAC) questionnaire among participants from the Singapore/Malaysia Cross-sequential Genetic Epidemiology Study (SMCGES). METHODS: Investigators administered the ISAAC survey questionnaire to SMCGES participants. Symptoms related to asthma were compared against diagnosed asthma, which was characterized by a questionnaire-reported history of asthma and exhibiting a positive skin prick reaction to allergen extracts from 2 dust mite species. Diagnostic accuracy was assessed via sensitivity (Se), specificity (Sp), positive and negative predictive values, and Youden's Index (J). RESULTS: This study analyzed data from 4,028 participants from Malaysia and 11,473 participants from Singapore. Asthma symptom prevalence differed between Malaysia and Singapore, with ever wheeze being the most prevalent in both populations. Diagnosed asthma was more prevalent in Singapore (17.3%, 95% confidence interval [CI]: 16.6-18.1%) than in Malaysia (9.7%, 95% CI: 8.8-10.7%). Ever wheeze showed the best diagnostic performance for diagnosed asthma in Malaysia (Se = 0.548, Sp = 0.831, J = 0.379) and Singapore (Se = 0.679, Sp = 0.888, J = 0.566). Combining symptoms or asthma medication usage improved accuracy slightly, with the most valid combinations being ever wheeze or exercise-induced wheeze in Malaysia (Se = 0.557, Sp = 0.824, J = 0.381) and usage of bronchodilators, beta-agonists, inhaled steroids, or leukotriene modifiers in Singapore (Se = 0.771, Sp = 0.871, J = 0.642). CONCLUSION: The modified ISAAC questionnaire used by the SMCGES showed good Se and Sp for diagnosed asthma, especially when combining various symptom indicators or usages of different asthma medications. These findings substantiate the continued use of the ISAAC questionnaire as a valuable survey tool in epidemiological studies across diverse populations.