Methacholine-induced Bronchial Hyperresponsiveness in Patients with Main Stem Endobronchial Tumor

Abstract

Background: Patients with main stem endobronchial tumor may have wheeze on physical examination, which mimics bronchial asthma. Objective: We evaluated the role of methacholine induced bronchial hyperresponsiveness, which is a hallmark of bronchial asthma, in differentiating these patients from patients with bronchial asthma. Methods: The provocative concentrations of methacholine required to reduce FEV1 by 20% of the pre-challenge baseline (PC20) and the prevalence of hyperresponsiveness were compared among patients with main stem endobronchial tumor (n=8), patients with symptomatic bronchial asthma (n=15) and normal healthy controls (n=10). Results: PC20 in patients with main stem endobronchial tumor (17.2+/-3.9 mg/mL) and normal healthy controls (23.9+/-3.2 mg/mL) were significantly higher than those in patients with bronchial asthma (6.3+/-2.3 mg/mL). Prevalence of hyperresponsiveness (PC20<25.0 mg/mL of methacholine) was higher in patients with bronchial asthma than that in patients with endobronchial tumor, or normal healthy controls (86.7% vs. 37.5%, 86.7% vs. 10.0%, P<.05 respectively). There were no significant correlations between clinical parameters (FVC, FEV1, peripheral blood eosinophil count, total IgE level) and PC20 in patients with main stem endobronchial tumor. Conclusion: It is reasonable to consider the possibility of endobronchial tumor in patients who have wheeze on physical examination, but do not have methacholine-induced bronchial hyperresponsiveness.