Clinical utility of exhaled nitric oxide fraction in the management of asthma and COPD

Abstract

Exhaled nitric oxide fraction (FENO) values can be easily measured using portable analysers and are a surrogate marker of airway eosinophilia.FENOmay be useful in diagnosing and monitoring conditions characterised by airway eosinophilia,i.e.asthma and possibly COPD. Many factors other than asthma and COPD affectFENO, especially atopy, which is associated with elevatedFENO. One guideline recommends thatFENOshould be used as part of the diagnostic pathway for asthma diagnosis in adults and children aged >5 years. The role ofFENOin monitoring asthma is even less clear, and most guidelines do not recommend its use outside of specialist asthma clinics. Currently,FENOis not recommended for diagnosis or monitoring of COPD. AlthoughFENOis starting to find a place in the management of asthma in children and adults, considerably more research is required before the potential ofFENOas an objective measurement in asthma and COPD can be realised.Key pointsFor individuals aged ≥12 years,FENOis not recommended by all guidelines as a test to diagnose asthma (recommended only by the UK National Institute for Health and Care Excellence guideline for asthma symptoms, which are likely to respond to corticosteroid treatment).FENOmay be used in conjunction with other investigations to diagnose asthma in 5–16-year-olds where there is diagnostic uncertainty, but further evidence is required.FENOis not recommended as a routine test to monitor all patients with asthma or to titrate asthma treatment.FENOis not recommended for routine clinical testing in adults with COPD.FENOmay be useful to identify patients with COPD who could benefit from the use of inhaled corticosteroids (asthma–COPD overlap).Educational aimsTo understand what factors other than asthma and COPD affectFENOTo understand the current controversies in the application ofFENOto diagnosis and management of asthma in childrenTo understand the current controversies in the application ofFENOto diagnosis and management of asthma and COPD in adults