BACKGROUND AND OBJECTIVE Airway hyperresponsiveness is a common feature of asthma. Methacholine and mannitol are two representative agonists for bronchial challenge. They have theoretically different mechanisms of action, and may have different diagnostic properties. However, their difference has not been directly evaluated among Korean adults. In this study, we compare the diagnostic properties of methacholine and mannitol bronchial provocation tests.

METHODS Asthmatic patients and non-asthmatic controls were recruited prospectively from four referral hospitals in Korea. Participants were challenged with each of methacholine and mannitol inhalation on different days. Their diagnostic utility was evaluated by calculating their sensitivity and specificity for asthma diagnosis. Response-dose ratio was also compared.

RESULTS A total of 50 asthmatic adults and 54 controls were enrolled (mean age 43.8 years). The sensitivity and specificity of mannitol challenge (defined by a PD15 of <635 mg) were 48.0% and 92.6%, respectively, whereas those of methacholine (defined by a PC20 of <16 mg/mL) were 42.0% and 98.1%, respectively. Twenty asthmatic participants (24%) showed positive response to a single agonist only. In the receiver operating curve analyses using response-dose ratio values, area under the curve was 0.77 (95% confidence interval (CI): 0.68-0.86) for mannitol, and 0.89 (95% CI: 0.83-0.95) for methacholine. The correlations between log- transformed mannitol and methacholine response-dose ratios were significant but moderate (r = 0.683, P < 0.001).

CONCLUSIONS The present study demonstrated overall similar diagnostic properties of two diagnostic tests, but also suggested their intercomplementary roles for asthma. The clinical trial registration number at ClinicalTrial.gov is NCT02104284.