Diagnosing asthma in primary and secondary care can still be challenging. Symptoms vary from person to person, they often overlap with other respiratory conditions and lung function tests do not always provide clear answers. Fractional exhaled nitric oxide FeNO testing offers clinicians the objective data they need to make earlier and more confident decisions.
Understanding FeNO
FeNO stands for fractional exhaled nitric oxide. Nitric oxide is produced naturally in the body and a small amount is present when we breathe. When inflammation is present in the airways, particularly type 2 or eosinophilic inflammation, nitric oxide levels increase. FeNO testing measures this increase.
The test is simple. The patient takes a deep breath and exhales steadily through a handheld analyser. The device measures the nitric oxide concentration in the breath and provides a numerical reading in parts per billion ppb. This makes FeNO one of the only rapid, non invasive tests that can directly assess airway inflammation.
Why FeNO matters
Traditionally, asthma diagnosis relied on medical history, symptoms and lung function tests such as spirometry. However, many asthma patients experience normal lung function between episodes or may not be able to perform spirometry reliably.
FeNO adds a missing piece to the diagnostic pathway. By showing whether inflammation is present at the time of testing, clinicians gain valuable information beyond symptoms and lung function patterns. This helps build a more complete and accurate picture of what is happening in the airways.
FeNO and type 2 inflammation
Asthma is not a single disease. For many people, symptoms are driven by type 2 airway inflammation. This inflammatory pattern involves eosinophils, cytokines and a cascade of biological processes that respond well to inhaled corticosteroids.
FeNO provides a direct way to detect type 2 inflammation and align treatment decisions accordingly.
A raised FeNO reading can suggest that:
-
Asthma is likely
-
Symptoms are inflammation driven
-
The patient is more likely to respond to steroid therapy
A normal or low FeNO can indicate alternative causes or help rule out asthma altogether when considered alongside other clinical findings.
How FeNO supports diagnosis
FeNO is valuable at multiple decision points in the diagnostic pathway.
FeNO helps clinicians:
-
Confirm inflammation when the diagnosis is uncertain
-
Differentiate asthma from other causes of breathlessness
-
Reduce the risk of misdiagnosis
-
Shorten the time taken to reach a treatment plan
-
Avoid unnecessary prescribing
This targeted use of therapy is not only clinically beneficial. It also supports stewardship of medication budgets across primary care, PCNs and ICBs.
FeNO works alongside spirometry
FeNO is not a replacement for lung function testing. Instead, it complements it.
Spirometry measures how the lungs move air. FeNO shows whether airway inflammation is present. Combining both provides a stronger foundation for diagnosis, particularly when spirometry is normal or borderline.
Clinicians who use FeNO in combination with spirometry report greater diagnostic certainty and fewer repeat appointments.
Making FeNO accessible in primary care
FeNO testing is quick, non invasive and easy to introduce. It requires minimal training and is suitable for adults and children aged five and over. Because results are available immediately, FeNO enables informed decisions during a single appointment.
FeNO fits naturally into:
-
Primary care asthma clinics
-
Community diagnostic hubs
-
Nurse led reviews
-
Secondary care follow up
When integrated into routine pathways, FeNO helps standardise asthma diagnosis and reduce variation in care.
Supporting better patient outcomes
For patients, a faster and clearer diagnosis means fewer delays and more targeted treatment. FeNO allows clinicians to identify inflammation early and intervene at the right time.
Better decision making leads to:
-
Improved symptom control
-
Fewer asthma attacks
-
Reduced urgent care visits
-
Increased adherence and engagement
As FeNO becomes a routine part of asthma assessment across the NHS, clinicians can provide care that is consistent, evidence based and aligned with national standards.
In summary
FeNO provides a clinically valuable way to measure airway inflammation, strengthen diagnostic pathways and guide treatment decisions. When used alongside history, symptoms and lung function tests, it offers a more complete picture of asthma and enables better patient outcomes across primary and secondary care.
Comments are closed.