Methacholine challenge is insufficient to exclude bronchial hyper-responsiveness in a symptomatic military population

Abstract

Background: Bronchial hyper-responsiveness in a military population has been evaluated by direct and indirect challenge methods. We hypothesized that negative methacholine challenge testing (MCT) was not sufficient to exclude significant bronchial hyper-responsiveness in a symptomatic military population with exertional dyspnea. The purpose of our study was to identify bronchial hyper-responsiveness in symptomatic military recruits and active duty personnel with normal baseline spirometry and negative pharmacologic bronchoprovocation testing. Methods: We performed a retrospective single center electronic chart review of symptomatic service members with a negative MCT who completed a subsequent exercise challenge test (ECT). Results: ECT was positive in 45 (26.4%) of 171 subjects (98 recruits). Subjects with a positive ECT had lower baseline forced expiratory volume in 1 second (FEV1), forced vital capacity (FVC) and FEV1/FVC than those with a negative ECT, and these differences were statistically significant. The mean drop in FEV1 with exercise challenge positive patients was 17.9 ± 9.2%, and the mean drop in FEV1 with MCT was significantly greater in exercise challenge positive patients (−9.5 ± 5.5 vs. −7.6 ± 5.5, p = 0.042). Exercise-induced bronchoconstriction (EIB) was observed in 41% of all recruits who subsequently did not complete training. Only 1 recruit subject of 28 with EIB completed training. Conclusions: Methacholine challenge is an insufficient screening test to detect bronchial hyper-responsiveness in a symptomatic military population. In military recruits, EIB is associated with training failure.

• Exercise challenge testing
• exercise-induced bronchoconstriction
• methacholine challenge testing
• military recruit

Acknowledgements

Dr Stocks collected and analyzed data, wrote and edited the main body of the text and abstract, and submitted the manuscript for publication. Dr Lin was the PI of the study and submitted the IRB protocol, collected and analyzed data, wrote and edited the text and provided general oversight of the study. Dr Tripp analyzed data, edited the text and prepared the manuscript for publication. The authors wish to acknowledge Dr Robert Riffenburgh, PhD, for statistical analysis and Ms Juneva Julio (CRT, CPFT) for assistance with data acquisition.