Clinical Characteristics of Asthmatics Having Negative Results to Methacholine Bronchial Challenge Test

Abstract

Background: The methacholine bronchial challenge test is widely used to evaluate airway hyperresponsiveness in asthmatics; however some studies have reported a few asthmatics have negative methacholine bronchial challenge test results. We investigated the prevalence and clinical characteristics of this group of patients. Methods: We retrospectively analyzed the medical records of 118 patients diagnosed as having asthma who visited the Allergy Clinic of Ajou University Hospital between March 2010 and February 2011. Patients were divided into 2 groups according to the methacholine bronchial challenge test results: group I included those with positive results (group I, n=92) and those with negative results (group II, n=26). Results: Of the 118 subjects, 26 (22.0%) showed negative methacholine bronchial challenge test results. The rates of late-onset asthma (65.4%), non-atopy (42.1%) and overweight (47.4%) were higher in group II than in group I (37%, P=0.013; 19.6%, P=0.008; and 23.9%, P=0.008). The baseline lung function and the frequency of severe asthma exacerbation were not significantly different between the 2 groups. Conclusion: In this study, 22% of the asthmatic patients diagnosed by allergy specialists had negative methacholine bronchial challenge test results. It is suggested that late-onset asthma, non-atopy and overweight may be characteristic findings.