Validity of FENO and small airway function indices in diagnosis of CVA

Background: The diagnostic value of Fractional exhaled nitric oxide (FeNO) in cough variant asthma (CVA) patients is poorly understood. Small airways remain an important aspect of CVA. The use of FeNO measurement or its combination with the small airway in differentiating CVA patients from chronic cough patients is not yet explored. Aims: The aims to explore the function of FeNO measurement, along with its combination to that of the small airways indices in the diagnosis of CVA. Methods: Patients with chronic cough that lasted for more than 8 weeks without any wheezing and abnormalities on X-ray or larger airways function were subjected to FeNO test, pulmonary function test and bronchial hyperresponsiveness test. ROC curves were obtained to evaluate the value of FeNO and small airways indices in CVA diagnosis. Results: A total of 450 patients were enrolled. The FeNO value in CVA was significantly higher than that in NCVA group [42(41) parts per billion (ppb) vs (16(11) ppb), P Conclusions: The measurement of FeNO is a noninvasive and sensitive method of differentiating CVA patients from NCVA patients. A combination of the level of FeNO and the abnormal small airway function suggested higher possibility of CVA;resulted in a rapid diagnosis and avoided the unnecessary treatments. This finding provide a new perspective for the management of patients with CVA.