ABSTRACT
Cough is one of the most common respiratory complaints leading to medical consultation. Fractional exhaled nitric oxide (FeNO) testing detects eosinophilic inflammation of the airway. We evaluated the diagnostic efficacy of FeNO testing in patients with cough. Patients who presented to the respiratory medicine department of our hospital with a chief complaint of cough and underwent FeNO testing were included in this study and divided into asthma and non-asthma groups. Patients with confounding factors such as allergic rhinitis and atopic predispositions were also identified and those with and without confounding factors, respectively, were further divided into the asthma and non-asthma groups. Median FeNO in the asthma and non-asthma groups was respectively 31 and 19 ppb in all patients and 31 and 18 ppb in those without confounding factors, with significant differences between the groups in both populations. The corresponding values in patients with confounding factors were 46 and 23 ppb, with no significant difference between the groups. A cut-off of 27 ppb differentiated between the asthma and non-asthma groups with sensitivity of 0.603 and specificity of 0.776. These results suggest FeNO testing is effective in the differential diagnosis of cough in patients without confounding factors.