Feasibility study of fractional exhaled nitric oxide in the dignosis of cough variant asthma

Abstract

Objective Evaluate the accuracy of fractional exhaled nitric oxide (FeNO) determination for the diagnosis of cough variant asthma(CVA) and determine the optimal cut point. Methods Collected 172 cases of chronic cough patients from October 2012 to October 2013 in the First Affiliated Hespital of Soochow University Hospital.Eighty of them were diagnosed with CVA patients and the other 92 were non-CVA,divided into the CVA group and the non-CVA.Astrograph Airway Responsiveness Analyzer and FeNO Tester were used to conduct the excitation experiment and FeNO concentration detection.Based on different FeNO cut point corresponding to specified degree of sensitivity and specificity,the ROC curve was plotted to assess the accuracy of Fe NO CVA diagnosis and its optimum cut point. Results FeNO value of CVA group[(41.04±18.41) ppb] was significantly higher than the non-CVA group[(23.60±16.58) ppb],and P< 0.01.Area under the ROC curve was 0.830 (CI:0.767~ 0.893),the optimal cut point of FeNO used to diagnose CVA is at 33 ppb,by which the value of sensitivity was 73.4% and specificity 81.0%,positive predictive value 77.9%,negative predictive value 78.9%,accuracy 78.5%. Conclusions FeNO used in the CVA diagnosis shows higher sensitivity and specificity,and it can be used as auxiliary diagnosis of CVA. Key words: Cough variant asthma; Fractional exhaled nitric oxide; Bronchial provocation tests; Receiver operating characteristic curve