Airway response to exercise measured by area under the expiratory flow-volume curve in children with asthma

摘要

Background The exercise challenge test is the gold standard for diagnosing exercise-induced bronchoconstriction; however, it produces negative results in many children with postexercise symptoms. Objective To assess the utility of the area under the expiratory flow-volume curve (Aex) to identify exercise-induced bronchoconstriction in children with asthma. Methods Data from the medical records of 221 children with asthma who underwent an exercise treadmill challenge (ETC) were analyzed. The relation between exercise-induced respiratory symptoms and results of the ETC were assessed, specifically, the maximal decrease in forced expiration in 1 second (FEV1) and the maximal decrease in the Aex. Results The receiver operating characteristic curve showed that a decrease greater than 6% in the Aex was an optimal cutoff point to produce the fewest misclassified ETC results based on a greater than 10% decrease in FEV1. The results of multivariable logistic regression showed that a decrease greater than 6% in the Aex was comparable to a decrease greater than 10% in FEV1 during an ETC and was more closely related to the presence of exercise-induced respiratory symptoms. Measuring the Aex during a routine ETC allowed a confirmation of bronchoconstriction in an additional 49 children (44%) with asthma and exercise-induced respiratory symptoms. The Aex measurement increased the sensitivity and negative predictive value of ETC without a significant effect on ETC specificity. Conclusion Measuring the Aex increases the sensitivity and negative predictive value of ETC without producing a significant change in ETC specificity. Applying a 6% decrease in the Aex as a cutoff point for a positive exercise challenge test result may prevent the underdiagnosis of exercise-induced bronchoconstriction in children with asthma and postexercise symptoms. Trial Registration This study was registered at www.clinicaltrials.gov (NCT01798823).