Use of fractional exhaled nitric oxide to guide the treatment of asthma and chronic cough

Fractional exhaled nitric oxide (FeNO) is a breath biomarker that is easy to perform at the point of care in individuals 5 years or older. Elevated FeNO levels indicate increased type 2 airway inflammation, specifically increased interleukin 4/13 activity. Recent guidelines have made recommendations on the utility of FeNO measurement in the diagnosis and management of asthma. Measurement of FeNO is recommended as an adjunct to the evaluation process in patients with suspected asthma in whom the diagnosis of asthma is uncertain based on clinical presentation, spirometry, and bronchodilator challenge testing. Elevated FeNO levels are associated with an increased risk of asthma exacerbation, and FeNO suppression test can help differentiate “difficult” from “severe” asthma. High FeNO levels can predict response to anti-inflammatory therapies, including corticosteroids and certain biologics. FeNO measurement also has value in evaluation of chronic cough with increased levels suggesting a corticosteroid responsive condition such as cough-variant asthma or eosinophilic bronchitis.