Spirometry is one of the most useful tests for patients in with wheeze, cough, dyspnoea, smoking-related risk, or possible occupational exposure. Yet its value depends on technical quality, operator skill, and interpretation that starts with the test itself (rather than the machine-generated label).

Poor-quality spirometry does not just produce questionable results; it can change the diagnosis. It can falsely reassure in suspected asthma cases, overcall COPD in older patients, or suggest restriction when the real issue is incomplete inspiration, early termination, or weak effort. While the numbers may look persuasive, the trace, quality grade, operator comments, and clinical context tell the real story.

The 2026 TSANZ Spirometry Suite for Australian Primary Care provides guidance for getting the most out of spirometry testing in primary care — and avoiding common pitfalls.

Case 1: Typical asthma symptoms but “normal” spirometry

A 28-year-old woman presents with intermittent wheeze, chest tightness, and cough, particularly with viral infections, cold air and exercise. She is asymptomatic on the day of review. Office spirometry is performed and the machine report is flagged as within normal limits.

False reassurance

The Australian Asthma Handbook is clear that normal spirometry does not exclude asthma, especially when the patient is asymptomatic at the time of testing. A technically sound normal study in an asymptomatic patient may leave asthma on the table, whereas a technically poor normal study may tell us very little.

A positive bronchodilator response can help confirm the diagnosis but repeat testing or further investigation may still be required if the history remains convincing.

The new TSANZ standards stress asking: “Was this an acceptable and repeatable test?”

Before deciding that spirometry results are normal, someone needs to know if:

• there was cough, leak or glottic closure
• the patient fully inspired before exhaling
• the effort was sustained long enough to produce a valid FVC
• the manoeuvres were acceptable
• the best values were repeatable

To meet the updated TSANZ standards for repeatability, both the best two FEV1 values and the best two FVC values must be within 150 mL of each other (or within 100 mL if the FVC is under 1.0 L). Operators must aim for quality grades A or B for both FEV1 and FVC, and the quality grade and technical comments must be documented – even when the required standard is not achieved.

In a patient like this, TSANZ spirometry standards advise reviewing the test quality, interpreting results, then deciding if bronchodilator responsiveness testing, repeat spirometry, or referral for respiratory laboratory testing is needed.

Case 2: Older smoker whose machine report says “obstruction”

A 71-year-old former smoker presents with exertional dyspnoea and a chronic morning cough. Spirometry is performed and the software-generated interpretation suggests airflow obstruction.

Allowing the software to interpret findings

The TSANZ Standards emphasise that a clinician should interpret the results, informed by test quality, z-scores, the lower limit of normal and clinical context. Auto-generated interpretations are not a substitute for this process. This is particularly important in older adults, where age-related physiological changes can make simplistic interpretation more misleading.

Z-scores provide a standardised way of understanding whether the result falls outside the expected range for age, height and sex, and help reduce overcalling of mild abnormality. Z-score-based interpretation forms part of the clinical workflow: confirm the test is technically acceptable and repeatable, interpret the pattern, then integrate the result with the patient’s history and presentation.

At most, treat the machine comment as a prompt to review the test. Before labelling COPD, the interpreter needs to ask whether:

• the flow-volume loop is believable
• the manoeuvres were acceptable and repeatable
• bronchodilator testing was performed appropriately
• the symptoms, smoking history and any occupational exposures fit the physiology

Where results are borderline, discordant, or difficult to reconcile with the clinical picture, repeat testing or referral for further assessment is often more helpful than trying to force certainty from a single office study.

Practice tip: Lung function severity is not the same as disease severity. Spirometry does not replace clinical judgement about impact, burden, or management.

Case 3: Chronic cough and a low FVC

A 57-year-old man is referred after office spirometry shows a low FVC with a preserved FEV1/FVC ratio. The report says possible restriction. He is now concerned that he may have pulmonary fibrosis.

Spirometry is not diagnostic of restriction

Spirometry may suggest a restrictive pattern, but spirometry alone does not diagnose restriction. The TSANZ Standards state that definitive diagnosis requires lung volume testing, typically in a specialist respiratory facility. It also recommends that symptomatic patients with an FVC below the lower limit of normal be referred for further lung function testing (such as DLCO and/or chest imaging).

The low FVC could also reflect technique rather than pathophysiology. Incomplete inspiration, premature termination, mouth leak, poor coordination, or weak effort can all produce a result that appears restrictive when it is not. This is why real-time coaching, quality assessment, and repeatability are so important

The right response to a low FVC is to ask whether the spirometry is believable, the pattern is reproducible, and whether referral for full lung function testing is needed. This approach can reduce unnecessary anxiety and make it easier to identify patients who need further work-up.

What changes in day-to-day practice

The new TSANZ standards frame spirometry as a clinical test that must be performed systematically to be reliable. It translates international spirometry principles into operational expectations for Australian primary care, setting out requirements for equipment, environment, infection control, patient preparation, quality control, test conduct and grading, bronchodilator testing, reporting, and interpretation.

The standards require a fit-for-purpose spirometer, proper maintenance, and regular calibration checks. If spirometry is performed daily, the calibration check should occur each day before testing. If testing is less frequent, it should occur on the day spirometry is performed. If the check fails, the spirometer should not be used until the problem is identified and resolved.

Practice tip: Patients must be prepared before the test, with a clear explanation that it requires maximal effort and repeated attempts. Bronchodilator responsiveness testing should be undertaken in a standardised way, with post-bronchodilator spirometry repeated at least 10 minutes after the final bronchodilator dose.

Operators should aim for a minimum of three acceptable manoeuvres, while no more than eight attempts should usually be needed before stopping and documenting why acceptable and repeatable results could not be obtained.

The report should include the largest acceptable FEV1 and FVC, the quality grade, and sufficient data and curves to allow the interpreter to judge whether the values are trustworthy. If the interpreting clinician can’t see if the manoeuvres were acceptable and repeatable, then the report risks looking more definitive than it really is.

Why updated standards for training and maintaining competency are also crucial

Trained operators make a real difference to spirometry results. If the patient has coughed early, terminated too soon, produced variable efforts, or not inhaled fully, the numerical result may look convincing but be clinically unreliable.

The TSANZ Standards for Training and Maintaining Competency explain that quality depends heavily on the person performing the test, noting spirometry competency must be developed, demonstrated, and maintained.

Initial training of at least 10 hours is required, with at least 60% of that time devoted to hands-on training. Formal assessment and successful completion of a post-course workplace portfolio are also required.

Refresher training should occur within 12 months of initial training and then at least every three years.

Making high-quality spirometry achievable in practice

Better spirometry should lead to greater diagnostic confidence and better-targeted management for patients with respiratory symptoms. The TSANZ Spirometry Suite of documents provide practical advice that delivers real clinical value in busy practice settings, acknowledging that it takes patient coaching, adequate time, quality checks, consumables, documentation, and actively maintaining skills.