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 $8.1{\pm}1.16mg/mL$, $16.9{\pm}2.21mg/mL$, and $22.0{\pm}1.47mg/mL$, 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 $PC_{20}$ value. Please check my changes.) at the new cut-off points of$PC_{20}{\leq}16mg/ml$, 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.

만성폐쇄성폐질환과 천식의 감별진단에서 메타콜린 기관지유발검사의 의의

연구배경: COPD 환자에서 천식을 동반한 환자들이 많이 있다고 보고 되어 있었고 기관지 과민성이 높은 비율로 보고되어 메타콜린 기관지유발검사가 이두 질환을 감별에 어떤 의의가 있는지 알아보았고, 치료에 대한 도움을 얻고자 연구하였다. 방 법: 전북대학교병원에서 2004년 1월부터 2004년 12월까지 메타콜린 기관지유발검사를 시행한 환자를 대상으로 전향적으로 연구하였다. 65명의 천식환자 23명의 COPD환자, 대조군에서 메타콜린 기관지유발검사를 분석하였다. 결 과: 각 군의 $PC_{20}$의 평균값은 천식군, COPD군 및 대조군에서 각각 $8.1{\pm}1.16$, $16.9{\pm}2.21$ 과 $22.0{\pm}1.47mg/mL$이고, 천식군, COPD군 및 대조군의 메타콜린 기관지유발검사의 양성율은 각각 65%, 30%와 9%였다. 메타콜린 기관지유발검사 양성 판정 기준을 $PC_{20}$ 16 mg/mL 이하로 가정할 때 천식군과 COPD군의 양성율은 80%와 30%이었고 민감도, 특이도, 양성예측률 및 음성예측률은 각각 80%, 75%, 78%와 78%였다. 결 론: 메타콜린 기관지유발검사의 양성기준을 $PC_{20}{\leq}16mg/mL$으로 하였을 때 천식 및 COPD가 동반된 천식과 순수한 COPD의 감별에 보다 많은 도움을 줄 것으로 예상되며 궁극적으로 COPD 환자들에게 보다 개별적이고 적절한 치료적 접근에 도달할 수 있도록 해주는 진단 방법 중 하나가 될 수 있다고 생각한다.