Chapter 5 – Exhaled Nitric Oxide as a Biomarker for Asthma Management

FeNO is an easily and quickly performed noninvasive measure of allergic airway inflammation, which can provide complementary information when used with spirometry and symptoms when determining asthma severity and control. FeNO levels are elevated in asthmatics with Th2-mediated inflammation, which comprise 80% of children and up to 60% of adults with asthma. FeNO is superior to FEV1 in predicting response to inhaled glucocorticoid therapy and several biologic agents such as omalizumab, dupilumab, and lebrikizumab. In addition, FeNO is superior to symptoms, PEF variability, and baseline FEV1 in diagnosing Th2-mediated asthma. FeNO is also superior to FEV1 in predicting loss of asthma control during tapering and/or withdrawal of inhaled GC therapy and is as effective, or superior to, FEV1, in predicting subsequent asthma exacerbations in patients with Th2-mediated asthma. Lastly, FeNO may serve as a diagnostic and predictive tool in preschool children at risk for asthma. Its limitations include being a marker for only Th2-mediated inflammation, insurance reimbursement, and whether FeNO can provide additional information to guidelines-based asthma management.