Clinical significance of methacholine bronchial challenge test in differentiating asthma from COPD

Background: Although airway hyper-responsiveness is one of the characteristics of asthma bronchial hyper-responsiveness has also been observed to some degree in patients with chronic obstructive pulmonary disease (COPD). Moreover, several reports have demonstrated that a number of patients have both COPD and asthma. The methacholine bronchial challenge test (MCT) is a widely used method for the detecting and quantifying the airway hyper-responsiveness, and is one of the diagnostic tools in asthma However, the significance of MCT in differentiating asthma or COPD combined with asthma from pure COPD has not been defined The aim of this study was to determine the role of MCT in differentiating asthma from pure COPD. Method: This study was performed prospectively and was composed of one hundred eleven patients who had undergone MCT at Chonbuk National University Hospital. Sixty-five asthma patients and 23 COPD patients were enrolled and their MCT data were analyzed and compared with the results of a control group. Result: The positive rates of MCT were 65%, 30%, and 9% in the asthma, COPD, and control groups, respectively. The mean PC ₂₀ values of the asthma, COPD, and control groups were 8.1±1.16 mg/mL, 16.9±2.21 mg/mL, and 22.0±1.47 mg/mL, respectively. The sensitivity, specificity, positive predictive value, and negative predictive value of MCT for diagnosing asthma were 65%, 84%, 81%, and 69%, respectively. The sensitivity, specificity, positive predictive value, and negative predictive value of MCT (ed note: please check this as I believe that these values correspond to the one PC₂₀ value. Please check my changes.) at the new cut-off points of PC₂₀ ≤ 16 mg/ml, were 80%, 75%, 78%, and 78%, respectively. Conclusion: MCT using the new cut-off point can be used as a more precise and useful diagnostic tool for distinguishing asthma from pure COPD.