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Airway hyperresponsiveness by methacholine challenge testing following negative exercise challenge.
Linda L Brown1, Bryan L Martin, Michael J Morris
1Allergy/Immunology Service, Department of Medicine, Madigan Army Medical Center, Fort Lewis, Washington, USA.
Summary
A significant number of patients with exertional dyspnea show positive results on methacholine challenge testing (MCT) even after a negative exercise challenge test (ECT). This suggests ECT may not be a reliable initial diagnostic tool for exercise-induced bronchospasm.
Area of Science:
- Pulmonology
- Respiratory Medicine
- Diagnostic Testing
Background:
- Exercise challenge testing (ECT) is often insensitive for diagnosing airway hyperreactivity.
- Previous research has not compared ECT to methacholine challenge testing (MCT) in a clinical setting.
Purpose of the Study:
- To assess the rate of positive MCT in patients experiencing exertional dyspnea.
- To evaluate patients with normal baseline spirometry and negative ECT results.
Main Methods:
- An observational study included 215 military patients with exertional dyspnea and normal spirometry.
- Patients underwent ECT; those with negative results were then tested with MCT.
- Bronchial hyperreactivity was defined by a 15% decrease in FEV1 postexercise.
Main Results:
- Of 128 patients with negative ECT, 52 (41%) had a positive MCT.
- A majority of positive MCT results (74%) occurred at low methacholine concentrations (≤2.5 mg/mL).
- ECT alone identified only 25 positive cases out of 82 tested.
Conclusions:
- A substantial proportion of patients with exertional dyspnea have positive MCT results despite negative ECT.
- The findings question the diagnostic value of ECT as a first-line test for exercise-induced bronchospasm.