Abstract: OBJECTIVE: To evaluate our experience with patients who presented with chronic cough and how exhaled nitric oxide predicted response to inhaled corticosteroid (ICS) therapy. METHODS: This retrospective observational study of 114 patients evaluated for chronic cough with measured exhaled nitric oxide and bronchodilatation test was conducted from Jan 1, 2010, through FENO Dec 31, 2010. Clinical records were extracted. Patients with FENO documented follow-up were contacted by telephone and administered a questionnaire. RESULTS: In 62 patients, ICS therapy was started or the current ICS dose increased. There were no difference in age, gender, body mass index (BMI), and FEV1%predicted, et al. Forty patients had elevated exhaled nitric oxide levels (48.13±15.66ppb), which were significantly higher than those of the others. Twenty-two patients with exhaled nitric oxide levels in the reference range were also prescribed ICS, and only 2 had cough improvement. Patients had documented followup that ranged from 4 weeks to 16 months. A cutoff of 34 ppb was found to best differentiate ICS responders and FENO responders. CONCLUSION: Measurement of exhaled nitric oxide accurately predicted response to ICS therapy for chronic cough. Patients with a positive exhaled nitric oxide test result had a strong likelihood of response to ICS, whereas a negative exhaled nitric oxide test result indicated an unlikely response to ICS. This finding may potentially have an impact on how patients with chronic cough are evaluated and treated.

Key words: Chronic cough, Exhaled nitric oxide, Inhaled corticosteroid, Bronchodilatation test