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The most convenient biomarker for enhanced asthma management

Nobel Prize-Winning Science

FeNO stands for fractional exhaled nitric oxide (NO). NO is a molecule produced by the lungs that can be measured in exhaled breath. The use of NO in medicine was a real breakthrough, leading to a Nobel Prize in 1998.

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Asthma: it’s about inflammation

Although asthma is traditionally diagnosed with tools that measure airway obstruction, it’s actually an inflammatory condition.1

As research progresses, opinion is changing. It is now understood that up to 85% of asthma patients have Type 2 airway inflammation.2

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"Type 2 airway inflammation seems to be particularly associated with asthma attacks. We know we can modify that with different treatments. So it isn't adequate now in the 2020s to just identify variable airflow obstruction. That's a good start, but you need to go beyond that.”

Professor Ian Pavord, University of Oxford

Type 2 airway inflammation

Type 2 inflammation is driven by T-helper 2 cells, which produce interleukins IL-4, IL-5 and IL-13. IL-4 and IL-13 upregulate nitric oxide levels in the lungs.3

Numerous studies have recognised FeNO as a helpful biomarker of airway inflammation.

Biomarkers: the future of asthma management

As knowledge of the underlying causes of asthma has evolved, diagnostic and management methods have too.

Biomarkers provide objective data on biologic parameters such as airway inflammation and disease activity. This can improve the understanding of asthma and lead to better patient outcomes.

Available right at the point-of-care, FeNO testing allows physicians to instantly assess airway inflammation and optimise patient therapy and adherence.

See inflammation more clearly with FeNO

Understanding the level of inflammation with FeNO can lead to improved asthma care. FeNO levels are elevated in asthma and can provide healthcare professionals with the opportunity to see inside a patient’s lungs at the point-of-care.

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Treatable traits

Treatable traits or modifiable risk factors, such as FeNO, are patient characteristics which can be addressed to personalise disease management.4 High FeNO is associated with a 4x greater risk of potentially severe exacerbations, and this is a treatable trait you can target to improve patient outcomes.5

More accurate diagnosis

With half of asthma cases misdiagnosed, lung function testing is not enough to make a decision. Asthma diagnosis is 7x more likely with a high FeNO level.6

This is Dan

Hypothetical patient reflecting typical clinical experience

He is 8 and was recently sent to the emergency department after suffering severe shortness of breath during a football match. A respiratory specialist suspected asthma but Dan's parents said he had no previous symptoms and doubted the diagnosis. A quick FeNO test revealed that Dan's FeNO level was 58.ppb. This shows high Type 2 inflammation and an increased risk of exacerbation. FeNO testing supported the asthma diagnosis and helped Dan's parents to visualise the risk. They then agreed to ensure Dan takes his inhaled corticosteroid every day.

Hypothetical patient reflecting typical clinical experience

Better management

A high FeNO level indicates a greater risk of exacerbation.5 Using FeNO testing as your asthma risk estimator can help reduce exacerbations by up to 50%.7

This is Julia

Hypothetical patient reflecting typical clinical experience

Her asthma symptoms were manageable but she had experienced some serious exacerbations in the last year, including a hospitalisation. She was reluctant to increase her steroid dose as she was worried about side-effects. As part of her management plan, Julia's FeNO was tested, revealing a FeNO level of 68.ppb. She was advised to take a higher ICS dose to bring the inflammation under control and avoid potentially severe exacerbations. Regular testing showed her FeNO was decreasing over time. After a year, Julia's symptoms resolved, her FeNO fell to 22.ppb and her ICS dose was safely stepped down.

Hypothetical patient reflecting typical clinical experience

Why measure FeNO?

FeNO testing is the most convenient way to assess airway inflammation at the point-of-care.


One test, one number. Airway inflammation in a single FeNO level.


Performing a FeNO test takes approximately one minute - quicker than making a cup of coffee.


Taking a FeNO test is as simple as inhaling and exhaling: no blood, sweat or tears required.

How to measure FeNO

Your patient performs the test by inhaling and exhaling into the NIOX VERO® breathing handle. After approximately one minute you are presented with a FeNO level. You can check this value with internationally recognised cut-off points from the American Thoratic Society to help decide your next treatment steps.8

Interpreting FeNO →     FeNO Guidelines →






Learn more about the gold standard FeNO testing device.

What about severe asthma?

Most international guidelines agree on the benefits of FeNO for the treatment of severe asthma. Research progresses very quickly and it is now known that both FeNO and blood eosinophils are beneficial to prescribe the right biologic treatment, reducing the likelihood of exacerbations. FeNO levels are also used to predict a good response to certain Type 2-targeted biologic treatments.1,9

Not only good for people, good for budgets

Studies have shown that FeNO testing is a cost-effective way to improve patient outcomes. Adding FeNO to the treatment algorithm can considerably reduce costs and improve quality of life when used in combination with current treatment guidelines.

Thousands of healthcare professionals around the world are enjoying the economic and clinical benefits of FeNO testing with NIOX VERO®.

Read our comprehensive review of health economics data about FeNO testing

FeNO is here to help you:3

Be more confident with asthma diagnosis

Speed up treatment decisions

Optimise ICS therapy and adherence

Identify appropriate biologics for severe asthma

Reduce severe exacerbations

Get started with NIOX VERO®

Join the thousands of healthcare professionals who have already performed over 40 million FeNO tests with NIOX®, and improve patient outcomes.


1. Global Initiative for Asthma (GINA). Global strategy for asthma management and prevention. 2021 update. 2. Heaney LG et al. Eosinophilic and noneosinophilic asthma: an expert consensus framework to characterize phenotypes in a global real-life severe asthma cohort. Chest. 2021;160(3):814-830. 3. Menzies-Gow A et al. Clinical utility of fractional exhaled nitric oxide in severe asthma management. Eur Respir J. 2020;55(3):1901633. 4. McDonald VM et al. Targeting treatable traits in severe asthma: a randomised controlled trial. Eur Respir J. 2020;55(3):1901509. 5. 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. 6. Wang Z et al. Agency for Healthcare Research and Quality (AHRQ). The clinical utility of fractional exhaled nitric oxide (FeNO) in asthma management. Comparative Effectiveness Reviews, 197. 2017. 7. Petsky HL et al. Tailoring asthma treatment on eosinophilic markers (exhaled nitric oxide or sputum eosinophils): a systematic review and meta-analysis. Thorax. 2018;73(12):1110-1119. 8. 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. 9. Holguin F et al. Management of severe asthma: a European Respiratory Society/American Thoracic Society guideline. Eur Respir J. 2020;55(1):1900588.

* Hypothetical patients