Webinar Debrief. Pulmonary Function Tests: A Critical Tool in the Patient Pathway

Why is lung function data becoming central to earlier diagnosis, better phenotyping, and more targeted treatment decisions?

Different physiological and biomarker assessments are now used across the patient pathway, from diagnosis and phenotyping to treatment selection and risk assessment. Read on to discover the key insights from Dr. Rory Chan’s webinar.

The Challenge: respiratory disease is becoming more complex

Respiratory pathways were once built mainly around diagnosis. Today, clinicians must also identify phenotypes, predict treatment response, prioritise patients for advanced therapies and intervene earlier. As precision medicine develops, healthcare systems need clearer ways to turn lung function data into clinical decisions.

Key insight 1: PFT is moving from diagnosis to disease phenotyping

Spirometry remains essential, but it does not tell the full story. Lung volumes and diffusing capacity of the lung for carbon monoxide (DLCO) can reveal patterns that spirometry alone may miss. Body plethysmography can show hyperinflation or air trapping, while DLCO provides insight into gas exchange.

Expert commentary

The shift is from asking, “Does this patient have obstruction?” to “What pattern of impairment is present, and what does it imply?” For example, obstruction with low DLCO may suggest emphysema, while preserved ratios with impaired gas transfer may indicate early ILD, pulmonary vascular disease, anaemia or another process requiring investigation.

Key insight 2: Biomarkers are changing treatment decisions

Fractional exhaled nitric oxide (FeNO) is a point-of-care marker of type 2 airway inflammation. In asthma, it can support diagnosis, monitor inflammatory activity and adherence, and help predict response to inhaled corticosteroids or biologic therapies.

Expert commentary

Biomarkers should complement, not replace, lung function testing. FeNO can identify inflammatory treatable traits, while spirometry, lung volumes and DLCO show functional impact. Together, they support more personalised decisions.

Key insight 3: Objective testing helps prevent misclassification

Respiratory symptoms can be misleading. Breathlessness, cough, wheeze, smoking history and imaging findings may suggest a diagnosis, but they do not confirm it. In suspected COPD, airflow obstruction should be confirmed objectively with spirometry, with post-bronchodilator measurement used to confirm diagnosis.

This matters because bronchodilator responsiveness, frequently used as a simple differentiator between asthma and COPD, can occur in both. Relying on single markers risks misclassification and inappropriate treatment escalation.

Expert commentary

The strongest diagnostic pathways are layered. They confirm disease objectively, then use additional physiological and inflammatory markers to refine severity, phenotype, and treatment direction.

Key insight 4: Lung function supports prognosis and earlier intervention

Pulmonary function testing also supports prognosis. Lung function trends can help identify patients at higher risk of deterioration before symptoms or exacerbations become obvious, providing earlier signals for monitoring, treatment escalation or specialist referral.

Examples include:

FEV1 contributes to risk prediction models used to estimate COPD exacerbations and hospitalisations.
DLCO can support surgical risk assessment and inform decisions around advanced respiratory interventions.
Longitudinal lung function trends may reveal disease progression earlier than symptom reporting alone.

Expert commentary

In precision respiratory care, a single measurement is rarely enough. Tracking physiological change over time can help clinicians recognise deterioration earlier and consider intervention before disease progression becomes more advanced.

What This Means in Practice

For healthcare organisations, integrating physiological data into care pathways can strengthen diagnostic confidence, support earlier intervention and help identify patients who may benefit from targeted therapies. Practical considerations include:

Embed pulmonary function testing throughout the patient pathway rather than using it only for diagnosis.
Expand access to advanced physiological testing and biomarker assessment.
Support multidisciplinary decision-making using objective respiratory data.
Focus on outcomes and treatment optimisation rather than isolated measurements.

The webinar cases showed that similar symptoms, and even similar spirometry findings, can conceal different disease processes. Additional physiological measurements can therefore reduce misclassification and support more appropriate treatment decisions.

Future Outlook

As respiratory diagnostics evolve, clinicians are likely to rely on broader combinations of spirometry, FeNO, body plethysmography, DLCO and maturing technologies such as oscillometry. The challenge will be integrating these data into care pathways in ways that improve decisions and outcomes.

Conclusion

Pulmonary function testing is evolving from a diagnostic checkpoint into a central tool for precision respiratory care. Better access to comprehensive testing can support earlier diagnosis, more accurate phenotyping, smarter treatment selection and more proactive care.