Methods: A prospective observational study was conducted in asthma-suspicious subjects. Indirect test was performed with skipped doses but up to 640 mg in accumulation. Methacholine inhalation (8mg/mL) by 2-min tidal breathing method was applied thereafter in the subjects who showed negative (PD15 > 640 mg of mannitol). Regardless of the results, at the end of the tests, bronchodilator was applied. AHR positive were defined as either PD15 < 640 mg of mannitol, PC20 < 8mg/mL of methacholine, or 20% increment of FEV1 in bronchodilator.
Results: Twenty four asthma-suspicious subjects (median age of 54, 11 males, 45.8%) were enrolled. The test-time test was theoretically shortened at least 10 min compared with that of suggested indirect test. In AHR, two subjects (8.3%) showed positive in mannitol provocation. Five (20.8%) showed positive in methacholine provocation compared with baseline FEV1 and 2 (8.3%) compared with FEV1 after 640mg of mannitol. Four (16.7%) showed positive in bronchodilator. Overall, 5 subjects (22.7%) showed AHR positive among 22 negatives in indirect test. No adverse reaction except for coughing during inhalation of mannitol was identified.
Conclusions: The sequential indirect-direct provocation facilitates to detect AHR in higher sensitivity and shorter test-time. As a confirmative test of asthma in clinical practice, it can be applied effectively after modification and verification.