Assessment of Bronchodilator Responsiveness Following Methacholine-Induced Bronchoconstriction in Children With Asthma

Purpose: The aim of this study was to investigate bronchodilator responsiveness (BDR) following methacholine-induced bronchoconstriction and to determine differences in BDR according to clinical parameters in children with asthma. Methods: The methacholine challenge test was performed in 145 children with mild to moderate asthma, and the provocative concentration causing a 20% decline in FEV1 (PC20) was determined. Immediately after the challenge test, patients were asked to inhale short-acting beta 2-agonists (SABAs) to achieve BDR, which was assessed as the change in FEV1% predicted x 100/post-methacholine FEV1% predicted. For each subject, the asthma medication, blood eosinophil count, serum total IgE, serum eosinophil cationic protein level, and skin prick test result were assessed. Results: The FEV1 (mean +/- SD) values of the 145 patients were 90.5 +/- 10.9% predicted, 64.2 +/- 11.5% predicted, and 86.2 +/- 11.2% predicted before and after methacholine inhalation, and following the administration of a SABA, respectively. The BDR did not differ significantly according to asthma medication, age, or gender. However, BDR in the atopy group (37.4 +/- 17.7%) was significantly higher than that in the non-atopy group (30.5 +/- 10.7%; P=0.037). Patients with blood eosinophilia (38.6 +/- 18.1%) displayed increased BDR compared with patients without eosinophilia (32.0 +/- 13.8%; P=0.037). Conclusions: In children with mild to moderate asthma, the responsiveness to short-acting bronchodilators after methacholine-induced bronchoconstriction was not related to asthma medication, but was higher in children with atopy and/or peripheral blood eosinophilia.