FeNO Testing in Asthma: A Practical Tool for Precision Care in the Community

Asthma is a heterogeneous disease, and one of the ongoing challenges in clinical practice is determining which patients are likely to benefit from anti-inflammatory treatment and which are not. Traditional tools—symptoms, spirometry, and peak flow—remain essential, but they do not always reflect underlying airway inflammation. Fractional exhaled nitric oxide (FeNO) testing helps address this gap.

FeNO testing, widely used internationally and increasingly adopted in community settings, provides a non-invasive measure of type 2 (eosinophilic) airway inflammation, offering actionable information at the point of care.

What Is FeNO?

FeNO measures the concentration of nitric oxide in exhaled breath. Nitric oxide is produced in higher amounts when eosinophilic airway inflammation is present, a key mechanism in many patients with asthma.

Unlike spirometry—which assesses airflow limitation—FeNO provides biologic insight into airway inflammation, making it a complementary, rather than competing, test.

Why FeNO Matters in Primary and Community Care

Several international guidelines now recognize FeNO as a useful adjunct in asthma management, particularly in primary and community-based settings.

FeNO can help clinicians:

• Support or refute a diagnosis of asthma when symptoms are non-specific

• Identify patients more likely to respond to inhaled corticosteroids (ICS)

• Detect poor adherence to anti-inflammatory therapy

• Guide escalation or de-escalation of treatment

• Reduce unnecessary corticosteroid exposure

This is particularly relevant in patients with:

• Chronic cough or episodic dyspnea

• Normal or borderline spirometry

• Poor symptom–lung function correlation

• Suspected non-adherence or steroid overuse

FeNO and Treatable Traits

Asthma management is moving toward a treatable traits model rather than a one-size-fits-all approach. FeNO fits squarely within this paradigm by helping identify type 2 inflammation, a trait that predicts response to corticosteroids and certain biologic therapies.

Importantly, a low FeNO does not exclude asthma, nor does a high FeNO confirm it in isolation. Interpretation must always occur alongside clinical assessment, spirometry, and history.

Practical Advantages of FeNO Testing

From a workflow perspective, FeNO testing offers several advantages:

• Non-invasive and well tolerated

• Rapid results (often within minutes)

• Minimal patient effort compared with spirometry

• Suitable for repeated measurements over time

Devices such as those produced by NIOX have standardized FeNO measurement and helped enable broader adoption across care settings.

What FeNO Does Not Replace

FeNO should not be viewed as a standalone diagnostic test. It does not replace:

• Clinical history and examination

• Spirometry and bronchodilator testing

• Assessment of comorbidities such as rhinitis, obesity, or reflux

Rather, FeNO adds a biologic dimension to assessment, supporting more nuanced, individualized decisions.

Integrating FeNO Into Community Respiratory Care

When integrated thoughtfully—alongside pulmonary function testing and clinical review—FeNO can improve diagnostic confidence, optimize treatment decisions, and support shared decision-making with patients.

For community-based diagnostics, this represents a shift toward precision respiratory care, closer to where patients live and receive most of their care.

Key Takeaway

FeNO testing is a practical, evidence-based tool that enhances asthma assessment by revealing underlying airway inflammation. Used appropriately, it supports more targeted treatment, reduces uncertainty, and aligns with modern, patient-centred models of care.

References (Selected)

1. Global Initiative for Asthma (GINA). Global Strategy for Asthma Management and Prevention.

2. National Institute for Health and Care Excellence (NICE). Asthma: diagnosis, monitoring and chronic asthma management.

3. American Thoracic Society. Clinical Practice Guideline: Interpretation of Exhaled Nitric Oxide Levels (FeNO).

4. Canadian Thoracic Society. Diagnosis and Management of Asthma in Adults.