Methacholine challenge testing (MCCT) and eucapneic voluntary hyperventilation (EVH) are two forms of bronchoprovocation testing used to diagnose asthma. EVH is reported to have a higher sensitivity for detecting exercise induced symptoms, while MCCT is very sensitive for detecting allergic and occupational disease. We wanted to compare performance characteristics for both tests in a military population presenting with asthma symptoms.
We identified individual patients who had both EVH and MCCT performed within the past 3 years. Demographic data, presenting complaints, spirometry, clinical diagnosis, and bronchoprovocation results were abstracted. Asthma diagnosed clinically by the ordering physician, along with a documented response to asthma specific treatment, was used as the gold standard.
42 patients were identified, with a mean age, BMI, and FEV1/FVC ratio of 34.5±12.2, 26.8±4.4, and 78.0±6.2 respectively. Overall prevalence of asthma, based on clinical diagnosis by the treating physician, was 25%. The most common presenting complaints were dyspnea (65.1%), exercise symptoms (62.8%), and cough (60.5%). Eight patients had a positive EVH, while only one patient had a positive MCCT. The average percent decrease on MCCT when EVH was positive was 8.9%±8.1% versus 7.2%±6.2% when EVH was negative (p = 0.52). Asthma was significantly more likely clinically when EVH was positive (p = 0.02), but not when MCCT was positive. Sensitivity, specificity, and positive and negative predictive values for EVH were 60.0%, 96.4%, 85.7%, and 87.1% respectively. Clinically confirmed asthma with exercise associated symptoms was also significantly more likely when EVH was positive (p = 0.004).
EVH and MCCT have different diagnostic performance characteristics in a group of patients with symptoms consistent with asthma. EVH was more accurate overall and in patients who complain of exercise related symptoms.
Patients suspected of having asthma who do not have a significant response to methacholine may require EVH to definitively rule out the diagnosis.
Brian Cohee, No Financial Disclosure Information; No Product/Research Disclosure Information