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Asthma Awareness Month Part 2: What is FeNO?


This is part two of our four-part series for Asthma and Allergy Awareness Month in the USA. Following on from covering What is Asthma last week, and some key facts, this week, we are looking at FeNO (fractional exhaled nitric oxide).

Part two: What is FeNO?

FeNO (fee-no) stands for fractional exhaled nitric oxide.

Nitric oxide is naturally produced in low levels in the lungs, but when inflammation is present, as seen with Type 2 asthma, levels can be much higher.1 For this reason, FeNO is a useful thing to measure to understand the level of inflammation present in your lungs, to help diagnose and manage your asthma.2,3

The best thing about measuring FeNO is that not only does it give you an accurate measure of your lung inflammation, but the test is simple, quick and non-invasive.4,5 The results are immediate which allows for quick diagnosis and treatment.6

FeNO testing gives a clear picture to the inflammation in your lungs, giving you a numerical value associated with the level of inflammation.1,3 The aim of asthma treatment, such as inhaled corticosteroids (ICS), is to bring your FeNO down to a healthy level.7

If you are worried you might have asthma, or that your asthma is not controlled, you can ask your doctor for a FeNO test.

We hope that this gives you a brief understanding to what FeNO is. If you have any questions, check out our handy printouts or ask your doctor about FeNO. Next week we will be looking at how FeNO can help you to manage your asthma.

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What is FeNO?

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Taking a test

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Supporting evidence:

1. Dweik RA et al. An official ATS clinical practice guideline: interpretation of exhaled nitric oxide levels (FeNO) for clinical applications. Am J Respir Crit Care Med. 2011;184(5):602-15. 2. Busse WW et al. Baseline FeNO as a prognostic biomarker for subsequent severe asthma exacerbations in patients with uncontrolled, moderate-to-severe asthma receiving placebo in the LIBERTY ASTHMA QUEST study: a post-hoc analysis. Lancet Respir Med. 2021;9(10):1165-1173. 3. Hanania NA et al. Measurement of fractional exhaled nitric oxide in real-world clinical practice alters asthma treatment decisions. Ann Allergy Asthma Immunol. 2018;120(4):414-418. 4. Carroll WD. NIOX VERO: Individualized Asthma Management in Clinical Practice. Pulmonary Therapy. 2016;2:171-88. 5. Alving K et al. Validation of a new portable exhaled nitric oxide analyzer, NIOX VERO®: randomized studies in asthma. Pulm Ther. 2017;3:207-218. 6. Czubaj-Kowal M et al. Relationship between air pollution and the concentration of nitric oxide in the exhaled air (FeNO) in 8–9-year-old school children in Krakow. International Journal of Environmental Research and Public Health. 2021;18(13):6690. 7. Asthma and Allergy Foundation of America (AAFA). FeNO tests to monitor FeNO levels. Available at; https://aafa.org/asthma/asthma-diagnosis/lung-function-tests-diagnose-asthma/feno-tests-to-monitor-feno-levels/. Accessed; Apr 2024.