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
