Metered-dose inhaler to deliver methacholine in bronchial provocation testing: a pilot study

Area of Science:

• Pulmonary Medicine
• Respiratory Physiology
• Diagnostic Testing

Background:

• Nonspecific bronchial provocation tests are crucial for diagnosing conditions like asthma.
• Current methods often rely on cumbersome nebulizer systems for methacholine delivery.
• Simplifying these tests with portable devices is desirable for clinical practice.

Purpose of the Study:

• To evaluate the feasibility of using a metered-dose inhaler (MDI) for methacholine delivery in bronchial provocation tests.
• To assess the accuracy of the MDI in diagnosing bronchial hyperresponsiveness (BHR).

Main Methods:

• An open, randomized crossover pilot study compared methacholine MDI delivery with a conventional nebulizer.
• The study involved 40 subjects (20 hyperresponsive, 20 nonhyperresponsive).
• The primary outcome was the provocative dose of methacholine causing a 20% fall in FEV1 (PD20 FEV1).

Main Results:

• The MDI test demonstrated high accuracy (97.5%) in diagnosing BHR when using a threshold of <800 microg.
• Results showed high concordance between the MDI and nebulizer methods for BHR diagnosis (Pearson chi2 = 36.19, p<0.0001).
• Nearly all subjects identified as hyperresponsive by nebulizer were also identified by the MDI.

Conclusions:

• A hand-held metered-dose inhaler (MDI) is a potentially suitable device for methacholine delivery in bronchial provocation testing.
• The MDI offers an accurate and convenient alternative for diagnosing bronchial hyperresponsiveness (BHR).
• Further validation in larger sample sizes is recommended to confirm these findings.