Background: Nonspecific bronchial provocation tests may be simplified by the use of hand-held devices to deliver methacholine.
Objective: To study the feasibility of using a metered-dose inhaler (MDI) to administer methacholine in bronchial provocation tests, and the ability of such a device to diagnose bronchial hyperresponsiveness (BHR) accurately.
Methods: In an open randomized crossover pilot study, we compared the provocative dose that induces a 20% fall in FEV1 (PD20 FEV1) obtained with the methacholine MDI with that obtained using a conventional nebulizer in 20 hyperresponsive and 20 nonhyperresponsive subjects. The MDI delivers 400 doses of 100 µg of methacholine, and was used via a spacer. Bronchial hyperresponsiveness (BHR) was defined as a PD20 FEV1 <2,000 µg with the conventional test using the nebulizer. The tests were performed in each subject in a randomized order, 1 to 7 days apart.
Results: Of the subjects who had a nebulizer PD20 FEV1 <2,000 µg, all but one had an MDI PD20 FEV1 <800 µg. When 800 µg was taken as the threshold for the diagnosis of BHR with the MDI test, the accuracy of this test to diagnose BHR was 97.5%, and the two tests were highly concordant for the diagnosis of BHR (Pearson χ2, 36.19; p<0.0001).
Conclusion: A hand-held device may be suitable for delivery of methacholine during bronchial provocation tests, if these results are confirmed in large samples.