Airway hyperresponsiveness by methacholine challenge testing following negative exercise challenge.
BACKGROUND
Exercise challenge testing (ECT) to diagnose exercise-induced bronchospasm has been demonstrated to be an insensitive screening test to demonstrate the presence or absence of airway hyperreactivity. Previous studies have not compared this procedure to methacholine challenge testing (MCT) in a clinical setting.


OBJECTIVE
To determine the frequency of positive MCT in subjects with exertional dyspnea, normal baseline spirometry, and negative ECT.


METHODS
Observational study of 215 military patients at an Army Community Hospital referred for evaluation of exertional dyspnea with normal baseline spirometry. Subjects were further evaluated with ECT on a graded treadmill with pre- and postexercise spirometry. Those without evidence of bronchial hyperreactivity as defined by a 15% decrease in FEV1 postexercise were evaluated with methacholine challenge testing (MCT).


RESULTS
Two hundred ten military subjects were evaluated. Eighty-two patients underwent ECT as the only method of bronchoprovocation testing with 25 positive tests (57 were negative but not referred for further testing). The remaining 128 patients with a negative ECT underwent MCT. Seventy-six (59%) had a negative MCT and 52 (41%) had a positive MCT. Of the positive MCT studies, 74% were positive at a methacholine concentration of 2.5 mg/mL or less.


CONCLUSIONS
Our study demonstrates that a significant number of patients being evaluated for exertional dyspnea will have a positive MCT after a negative ECT. Our findings lead us to question the utility of ECT as an initial diagnostic test for the exercise-induced bronchospasm.
Brown
Linda L
LL
Allergy/Immunology Service, Department of Medicine, Madigan Army Medical Center, Fort Lewis, Washington, USA.
Martin
Bryan L
BL
Morris
Michael J
MJ
D000328:Adult; D001986:Bronchial Spasm / Q000175:diagnosis*; D016085:Bronchoconstrictor Agents; D005080:Exercise Test; D005188:False Negative Reactions; D005260:Female; D006801:Humans; D008297:Male; D016210:Methacholine Chloride
D016085:Bronchoconstrictor Agents; D016210:Methacholine Chloride