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What is FeNO?

FeNO (Fractional exhaled Nitric Oxide) are very miniscule particles of the gas Nitric Oxide (NO), measured in parts per billion. NO is naturally produced by your body to help combat inflammation and when your airway is inflamed, NO is produced in the lungs and exhaled on the breath. The production of nitric oxide is often found to be higher in inflammatory conditions such as asthma and therefore FeNO measuring can be used for the detection and management of such conditions1, but also to differentiate between COPD, ACOS other and interstitial lung diseases that are not assessed by other means, such as lung function2.

Airway inflammation is a central process in asthma and other lung diseases3. Being able to detect eosinophilic airway inflammation and monitor a patient’s response to treatment is regarded as a gold standard in the management of respiratory diseases. Nitric oxide measurement is not intended as a stand-alone method for diagnosis and should be used in conjunction with other evaluation methods and tests4. Using FeNO measurements to evaluate airway inflammation in asthma represents a significant advance in respiratory medicine5, but until now this has been an expensive test to deliver in everyday practice.

Pathology of Asthma

FeNO in Asthma

Asthma is commonly referred to as an inflammatory disease which affects a person’s airways, leading to hyper-responsiveness, obstruction, mucus hyper-production, and airway wall remodelling9. Although airway eosinophilic inflammation is a key characteristic of asthma, very few methods are available for measuring airway eosinophilic inflammation. Airway eosinophilic inflammation can be measured, by measuring eosinophils and eosinophilic cationic protein (ECP) in sputum, or ECP’s can be measured in a blood sample10. These methods are commonly considered gold standard, but are very time consuming, expensive, and are not commonly readily available. A majority of asthma patient’s airway inflammation is allergen-driven Th2 response11. There is significant evidence from external literature suggesting FeNO (Nitric oxide) is a key biomarker tool for inflammation of the respiratory tract11.
Increased levels of FeNO in asthma are thought to come from inducible NOS2 expressed in the inflamed airways11. NObreath® offers an alternative aid to diagnose asthma, which is non-invasive, and significantly more cost effective than current gold standard methods diagnose airway eosinophilic inflammation, further in the diagnosis of asthma. As a result of substantial amounts of literature supporting FeNO measurements as an effective biomarker for asthma and other airway inflammation, FeNO breath testing is now recommended in NICE guidelines as an aid to diagnose allergic asthma12. Literature also suggests the ability for FeNO measurement to be used as good management tool for asthma13, assessing the effectiveness of treatments for patients, optimising asthma treatments.

Benefits of FeNO use

  • Non-invasive, quick and easy to perform5
  • Shows patient’s response to treatment, enabling the correct prescription of medication and safer/monitored adjustments
  • Aids in identifying patients who do/do not require on-going treatment6
  • Shows patient compliance
  • Shown to be superior to the majority of conventional tests of lung function, such as peak flow recording and spirometry5
  • Aids in differentiating between allergic (eosinophillic) and non-allergic asthma7.