Accurate methods that can be used to detect asymptomatic children with asthma in schools are lacking. Small airway dysfunction is a precursor of asthma. The objective of this study was to use the electronic nose (E-nose) to detect small airway dysfunction in elementary schoolchildren at risk of asthma and evaluate the acute effects of air pollution on respiration. We conducted this study in an elementary school. The study recruited 40 asymptomatic students with a history of asthma and 40 age- and sex-matched children without a history of asthma to take the breath test. We used an E-nose to analyze volatile metabolites and gas chromatography-mass spectrometry to analyze common air pollutants in exhaled breath. After excluding eight subjects in pilot tests, we included 72 subjects in the final analysis of the breath test. The sensitivity of detecting small airway dysfunction with the E-nose was 0.92, the specificity was 0.95, the positive predictive value was 0.79, the negative predictive value was 0.98, the overall accuracy was 0.94, and the leave-one-out cross-validation accuracy was 0.74. The area under the curve was 0.98 (95 % confidence interval: 0.96-1.00). Methyl tert-butyl ether was the only ambient air pollutant that had a significant negative correlation with the maximum mid-expiratory flow (r = -0.33, P < 0.05). The E-nose is highly accurate at detecting small airway dysfunction in children at high risk for asthma. An analysis of exhaled breath can also be used as a personal monitoring method to assess the acute effects of air pollution on respiration.
