The latest UK asthma guidelines1 clearly define the role of Fractional exhaled Nitric Oxide (FeNO) testing in both diagnosing and managing asthma over time. Backed by up-to-date clinical evidence and strong cost-effectiveness data, these recommendations are designed to support more accurate, efficient care across the board.
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But what does that look like in practice, especially for the individual navigating day-to-day life with asthma?
Let’s take a look at an example. Meet Ramila. She is 19 years old and visits her doctor complaining of chest tightness, wheezing, and shortness of breath.
Initially, it was primarily tied to exercise, but now it occurs more frequently, and Ramila recognizes it, especially when she wakes up in the morning. Ramila has avoided seeing her GP as it has not been a consistent issue.
Ramila recalls having an inhaler, a blue one, when she was younger, but has never had a formal diagnosis of asthma. Her older brother has asthma, and so does her aunt. Ramila has never experienced hay fever or eczema symptoms, has no allergies, and is otherwise healthy.
The GP listened to Ramila's chest, which sounded normal. However, just because she is asymptomatic doesn’t mean asthma can be ruled out. Ramila's GP has access to FeNO at the clinic, so they are able to do a FeNO test during this session.
The result came back as 61 parts per billion (ppb), which, given Ramila's history and symptoms, is consistent with an asthma diagnosis. According to the latest guidelines, a single test is enough to confirm an asthma diagnosis, and Ramila can begin treatment immediately.
If the GP did not have access to FeNO or there was a delay in receiving the test, they could also have ordered a blood test to determine Ramila's eosinophil count. Yet, this would mean a delay in diagnosis and possibly treatment until the test was processed, as this is not a near-patient test.
It was also possible that Ramila would have needed to schedule another appointment, putting further strain on primary care services and her already hectic schedule.
Once asthma is confirmed, Ramila can begin treatment. If her symptoms were only occasional, the recommended approach would be an Anti-Inflammatory Reliever (AIR) regimen. This involves using a combination inhaler that contains Formoterol and an inhaled steroid on an as-needed basis to relieve symptoms while also addressing inflammation.
However, since Ramila is experiencing symptoms daily, a Maintenance and Reliever Therapy (MART) regimen would be more appropriate. This still uses a Formoterol-containing combination inhaler, but with a different schedule: it’s taken regularly each morning and evening, and additionally as needed for symptom relief.
Notably, short-acting bronchodilators are not required with either the AIR or MART approach.
When it comes to choosing an inhaler device, a dry powder inhaler should be the first option, provided Ramila can use it correctly. These devices are not only effective but also have a significantly lower carbon footprint.
Ramila would need to be shown how to use the inhaler device properly, educated about asthma and how the drug works, and begin developing a personalized asthma action plan with the clinician.
This will help Ramila understand what good asthma control looks like and what medications she should take to achieve it. It will also assist her in identifying any deterioration in her symptom control and when urgent advice is required.
The plan should include who Ramila should contact, when her symptoms should be less effectively controlled, and what to do in an emergency. This is also an excellent chance to provide general health advice on smoking, alcohol, weight control, and leading an active lifestyle.
Ramila will be invited to attend regular reviews. The guidelines suggest this as a good time to check a FeNO level. It is also a good opportunity to reaffirm patient education, and FeNO is a useful tool for determining whether the current treatment regimen is controlling airway inflammation or not.
If the FeNO level is raised, it brings up a discussion about Ramila's understanding of the asthma diagnosis and how her prescribed inhalers work.
When Ramila had her FeNO examined, it seemed that it had crept up to 52 ppb from around 18 ppb.
After a discussion, it became evident that Ramila had gotten more complacent about her asthma and was using her inhaler less frequently. She had been using it only when she needed it, but on reflection, she realized that her symptoms were not as well controlled as they had been.
FeNO is an effective technique for identifying medication nonadherence and initiating a non-judgmental discourse. The guidelines also recommend monitoring FeNO before and after changing medications.
It can help decide which treatments are appropriate and assess treatment response. This is especially pertinent when Ramila returns with poor asthma control a few years later. She has good inhaler technique and has been following her MART regimen with good adherence. Regardless, her symptoms are worsening.
At a prior review, she was moved from a low-dose MART regimen to a moderate-dose MART regimen (with an increase in the steroid dose of the combo inhaler), which had been treating her symptoms for some time until recently.
In this case, the guidelines recommend measuring FeNO to help guide the next treatment option. Ramila's FeNO level was found to be normal (21 ppb), but as her symptoms worsen, she will require more medication.
With a normal FeNO level (showing that eosinophilic airway inflammation is under control), the clinician is advised to add extra treatment. This could include taking Montelukast orally once a day in addition to the MART regimen or using a Long-Acting Muscarinic Antagonist (LAMA) as inhaled therapy.
Ramila discussed the alternatives, benefits, and probable adverse effects before deciding to take Montelukast. If Ramila had a higher FeNO level, the treatment prescription would have been to continue anti-inflammatory therapy.
The alternatives here are to give high-dose inhaled steroids or to start biologic therapy. Both possibilities would be evaluated, and decisions would be made in consultation with Ramila and a respiratory physician, thus Ramila would require a referral for this. Without FeNO to guide decisions, a referral may be delayed needlessly.
It is also worth thinking about how to reduce asthma treatments; asthma is a changeable condition, thus treatment must be titrated up and down during periods of variance.
If Ramila had been on a moderate-dose MART regimen and remained symptom-free for at least three months—with no exacerbations and no need for additional rescue doses—this would suggest good asthma control. In that case, it might be appropriate to consider stepping down to a low-dose MART regimen by reducing the steroid component in her combination inhaler.
FeNO testing can be a valuable tool in guiding this decision, especially if the patient meets the criteria for well-controlled asthma. If Ramila’s FeNO level were low, indicating that eosinophilic airway inflammation was well managed, it would be a good time to discuss reducing the steroid dose, assuming she wasn’t approaching a time of year when her symptoms are typically triggered.
On the other hand, if her FeNO result were even moderately elevated, suggesting ongoing inflammation, stepping down the inhaled steroid wouldn’t be advisable.
While FeNO testing is often associated with asthma diagnosis, the latest UK guidelines highlight its value throughout the entire patient pathway. Its role extends well beyond diagnosis, supporting treatment decisions and ongoing management.
Ensuring easy, timely access to FeNO testing in primary care can significantly improve the accuracy and quality of care for people presenting with asthma symptoms.
FeNO testing with NObreath®
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Acknowledgments
This article is based on materials originally authored by Carol Stonham.
References
- National Institute for Health and Care Excellence (2024). Overview | Asthma: diagnosis, monitoring and chronic asthma management (BTS, NICE, SIGN) | Guidance | NICE. (online) NICE. Available at: https://www.nice.org.uk/guidance/NG245.
About NObreath
The NObreath® is a FeNO device by Bedfont® Scientific Ltd. which can be used to measure airway inflammation for the management and diagnosis of asthma.
Our mission is to help improve asthma diagnosis & management of adults and children worldwide through FeNO measuring. Our purpose is to make FeNO measuring more accessible globally, with the creation of an effective yet cost-efficient FeNO device and equally low cost consumables.
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