Response to Bronchodilators After Exercise Challenge Predicts Bronchial Hyperreactivity

Abstract

Background. Some subjects with suspected asthma and a negative exercise challenge test (ECT) demonstrate improved expiratory flow rates after administration of bronchodilators (BD) at the end of the ECT (unpublished observation). This study investigated whether this response predicts the presence of bronchial hyperreactivity (BHR). Patients and methods. The study population included 133 young adults (29.4% women) 21.1 ± 4.2 years of age who underwent ECT and a methacholine challenge test (MCT). A receiver-operator-characteristic curve was used to calculate the optimal cutoff level of the response to BD as a predictor of BHR according to MCT. Results. Using a MCT cutoff level of PC₂₀ ≤ 4 mg/mL showed BHR in 12.8% of subjects. Failure to improve FEV₁ by 8% after BD administration predicted the absence of BHR with sensitivity, specificity, and positive and negative predictive values of 76.5%, 68.4%, 25.3%, and 95.5%, respectively. Avoiding MCT in subjects with less than 8% response to BD would have saved 62.5% of the MCTs and would have missed only four (3%) patients with BHR. Conclusions. BD should be administered routinely after ECT, as the response may be used as a simple, inexpensive tool to predict BHR in young patients and may substantially reduce the number of unnecessary MCTs

Keywords:

• bronchial asthma
• bronchial hyperreactivity
• exercise challenge test