Pillai, S.M.

Abstract Rationale Bronchial hyperreactivity (BHR) is a hallmark of asthma, frequently presenting as exercise-induced dyspnea in children and adolescents. Identifying BHR is essential for accurate diagnosis and management of exercise symptoms. The methacholine challenge test (MCT) is the gold standard for diagnosing BHR due to its high sensitivity in detecting airway hyperresponsiveness. However, the MCT requires specialized equipment and stringent protocols, which can limit its availability and use in some clinical settings. An alternative approach, the bronchodilator response test (BDR), is more accessible and assesses the reversibility of airway obstruction following bronchodilator administration. BDR testing is a routine component of asthma diagnostics for evaluating airflow limitation, making it a potentially useful tool for BHR assessment. However, the ability of BDR testing to reliably detect BHR in exertional dyspnea is still uncertain. Prior research has shown that BDR testing, while specific, has low sensitivity for BHR when compared to the MCT, raising questions about its standalone utility in clinical practice. The objective of this study was to evaluate the diagnostic performance of the BDR in detecting bronchial hyperreactivity in exertional dyspnea, using the MCT as the reference standard. By analyzing sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV), we aimed to assess whether BDR testing could serve as a reliable alternative to MCT for diagnosing BHR. Methods We conducted a retrospective study of pediatric patients who underwent cardiopulmonary exercise testing, BDR, and MCT as part of their assessment for exertional dyspnea from July 2020 to February 2023. Patients up to 18 years of age were included. A positive BDR was defined by a 10% or greater improvement in FEV1% or FVC%, while a positive MCT was defined by a 20% reduction in FEV1%. Data are presented in a 2x2 table, with the MCT as the reference standard. Results and Conclusion In a cohort of 98 patients, 20 underwent both bronchodilator and methacholine testing. The BDR test, using MCT as the reference, showed a sensitivity of 16.7%, specificity of 87.5%, PPV of 66.7%, and NPV of 41.2%. These results suggest that, due to its low sensitivity, BDR testing alone is insufficient for BHR detection when clinical suspicion of asthma is high. The MCT remains the preferred diagnostic method, though using both tests may provide a more comprehensive evaluation of airway reactivity in children presenting with exercise symptoms.