Patient guide · Respiratory · 4 min read
Bronchodilator reversibility assessment, the spirometry test that distinguishes asthma from COPD.
Bronchodilator reversibility testing measures spirometry before and after inhaled salbutamol — the diagnostic test that distinguishes asthma (reversible obstruction) from COPD (irreversible obstruction). Foundation of respiratory diagnosis.
Key facts
- 01
Definition
Pre and post-bronchodilator spirometry — the paired measurement that defines reversibility.
- 02
30–45 minute test
A single clinic visit including baseline spirometry, salbutamol, wait and post-BD spirometry.
- 03
400 mcg inhaled salbutamol
Four puffs via spacer — the standard reversibility challenge dose used across UK and international guidelines.
- 04
Significant reversibility
A rise in FEV1 of ≥ 12% AND ≥ 200 mL after the bronchodilator — the diagnostic threshold.
- 05
Complements FeNO and eosinophils
Read alongside FeNO and blood eosinophils to build a rounded asthma diagnosis.
- 06
Foundation of asthma/COPD dx
The single test that most cleanly separates reversible (asthma) from irreversible (COPD) obstruction.
How it’s done
From consultation to plan — what happens, in order.
A single 30–45 minute visit: baseline spirometry, inhaled salbutamol, a short wait, repeat spirometry, then a written plan.
- 01
Before
Respiratory consultation
Focused history, examination and pre-test bronchodilator washout instructions.
- 02
On the day
Baseline spirometry
Three technically acceptable, reproducible flow-volume loops recorded pre-bronchodilator.
- 03
On the day
Inhaled 400 mcg salbutamol
Four 100 mcg puffs of salbutamol delivered via spacer under supervision.
- 04
On the day
15–20 minute wait
A short interval to allow full pharmacological effect before repeat testing.
- 05
On the day
Post-bronchodilator spirometry
The same set of manoeuvres repeated to reproducibility criteria.
- 06
On the day
Reversibility calculated
Change in FEV1 in mL and as a percentage of baseline, against the ≥ 12% and ≥ 200 mL threshold.
- 07
After
Structured plan
Written report and a plan — inhaled therapy, biologic pathway, pulmonary rehab or onward MDT review as needed.
Total time in the clinic: 30–45 minutes, plus your consultation.
What it shows
The patterns bronchodilator reversibility reveals.
The pre and post-BD numbers describe a specific physiological picture — reversible or fixed, obstructive or mixed — that anchors the diagnosis and the plan.
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FEV1 reversibility (%)
The proportional change in forced expiratory volume in one second after the bronchodilator.
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FVC reversibility (%)
Change in forced vital capacity — a secondary marker of air trapping and small-airways response.
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FEV1/FVC ratio
The obstructive index — persistently below 0.7 post-BD supports fixed obstruction.
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Post-BD FEV1 (% predicted)
Anchors severity grading in COPD and residual burden in partially reversible asthma.
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Response pattern (asthma vs COPD)
Significant reversibility favours asthma; a non-reversible obstructive pattern favours COPD.
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Small airways disease
Reduced FEF25–75 with preserved FEV1 flags distal airway involvement.
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Restrictive pattern flag
A reduced FVC with a preserved ratio raises restriction — prompts lung-volume testing.
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Red flag: severe fixed obstruction — pulmonary rehab + LVRS pathway
Post-BD FEV1 below 30% predicted with no reversibility warrants an advanced-COPD pathway.
Next steps
What follows the result.
The pattern picks the pathway — inhaled controller therapy, biologics, pulmonary rehabilitation, smoking cessation or MDT review.
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Inhaled corticosteroid + LABA (asthma)
The foundation controller for reversible obstruction with an asthma phenotype.
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LAMA + LABA (COPD)
First-line dual bronchodilation for symptomatic COPD without frequent exacerbations.
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Biologic therapy (severe eosinophilic asthma)
Anti-IL5, anti-IL5R or anti-IgE agents for severe asthma with a T2-high phenotype.
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Pulmonary rehabilitation
Structured exercise and education — the highest-value intervention in symptomatic COPD.
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Smoking cessation
The single intervention that most alters the natural history of COPD.
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Vaccination programme
Influenza, pneumococcal and COVID-19 vaccines reduce exacerbations and hospitalisation.
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Structured respiratory follow-up
Serial spirometry, symptom scores and inhaler technique review at defined intervals.
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Multi-disciplinary team review
Complex or severe disease reviewed jointly by respiratory, physiotherapy and specialist nursing.
Red flags
When the result changes what happens next.
Certain physiological patterns and clinical pictures escalate the pathway — targeted imaging, specialist referral or advanced-disease review.
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Severe fixed obstruction
Post-BD FEV1 below 30% predicted with no reversibility — advanced-COPD pathway.
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Alpha-1 antitrypsin deficiency
Early-onset or basal emphysema — a targeted serum test and specialist referral.
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Post-tuberculosis obstruction
Fixed obstruction with a TB history — imaging and MDT review to exclude sequelae.
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Bronchiolitis obliterans
Progressive fixed small-airways obstruction — cross-sectional imaging and specialist input.
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Persistent asthma despite triple therapy
Ongoing symptoms on ICS/LABA/LAMA — a severe-asthma clinic referral.
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Nocturnal symptoms with peak flow variability
Diurnal PEF variation with night-time wake — a classical uncontrolled-asthma picture.
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Occupational asthma
Symptoms with a workplace pattern — serial peak flows and occupational health input.
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Post-COVID small airways disease
New obstructive or mixed spirometry after COVID-19 — respiratory review with imaging.
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Vocal cord dysfunction masquerading as asthma
Inspiratory flow-volume loop truncation — ENT/speech-therapy assessment.
Sources
The guidelines that shape this guide.
Reviewed by Pulse Atlas Editorial Board (). Published 2026-07-30. Next review 2027-07-30.
A quiet reminder
This is a patient guide — not a substitute for clinical advice.
If your symptoms are new, sudden or worsening, speak to your respiratory clinician or GP.
- 01 Reference
British Thoracic Society / NICE. Asthma: diagnosis, monitoring and chronic asthma management (NG80).
British Thoracic Society / NICE. Asthma: diagnosis, monitoring and chronic asthma management (NG80). - 02 Reference
Global Initiative for Chronic Obstructive Lung Disease (GOLD). Global strategy for the diagnosis, management, and prevention of COPD.
Global Initiative for Chronic Obstructive Lung Disease (GOLD). Global strategy for the diagnosis, management, and prevention of COPD. - 03 Reference
European Respiratory Society. Technical standards on spirometry and bronchodilator reversibility.
European Respiratory Society. Technical standards on spirometry and bronchodilator reversibility. - 04 Reference
American Thoracic Society. Standardization of spirometry.
American Thoracic Society. Standardization of spirometry.
Frequently asked
Everything we get asked about bronchodilator reversibility testing.
Quick answers on what the test measures, how long it takes, the diagnostic threshold, how to prepare, and how it fits with FeNO and eosinophils.
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What is a bronchodilator reversibility test?
A paired spirometry test — measured before and after inhaled salbutamol — that quantifies how much a person’s airflow obstruction improves with a bronchodilator. It is the diagnostic test that most cleanly separates reversible (asthma) from irreversible (COPD) obstruction.
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How long does the test take?
Between 30 and 45 minutes in total. Baseline spirometry takes about 10 minutes, then 400 mcg of inhaled salbutamol is given, then a 15–20 minute wait, then the spirometry is repeated.
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What counts as a significant response?
An increase in FEV1 of at least 12% AND at least 200 mL from baseline. Both criteria must be met — a large percentage change on a very small baseline volume is not enough on its own.
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Do I need to stop my inhalers beforehand?
Yes — short-acting bronchodilators are usually held for 4–6 hours, long-acting for 12–24 hours, and ultra-long-acting for 36–48 hours. Your clinician will send an exact list ahead of the appointment.
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Is the test safe?
The test is very well tolerated. Salbutamol can cause a mild tremor or a briefly faster heart rate that settles within minutes. The forced blow itself is short-lived and safe.
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How does it fit with FeNO and blood eosinophils?
Reversibility measures the airflow response; FeNO measures airway inflammation; blood eosinophils flag a T2-high phenotype. Together they build a rounded asthma diagnosis and help select biologic therapy where appropriate.
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In practice, in London
What reversibility assessment looks like on the ground in London
With reversibility assessment, the London question is usually about report turnaround and the radiologist reading it — not whether the scan is available. On the NHS, reversibility assessment typically sits behind a triage step and a wait that can stretch from a few weeks into months. In London’s private sector, the same appointment often lands within days. That speed matters when symptoms are disrupting work, sleep, or a plan you’d already committed to — and it’s the single most common reason people call us in the first place.
A private reversibility assessment pathway in London usually looks like this: an initial consultation, any diagnostics booked at a nearby facility (most within Zone 1 or 2), and a written report sent to you and your GP within a few days. The consultants we work with hold NHS posts alongside their private lists, which keeps the standards consistent across both settings. For reversibility assessment specifically, the difference between a routine report and a sub-speciality read is where private care earns its keep.
Honesty about expectations is part of the job. A private reversibility assessment appointment in London won’t change the underlying medicine — the guidelines, the consultants, and the equipment are largely the same as on the NHS. What it changes is speed, continuity, and the amount of time you get to actually talk through the findings. Everyone we route to is GMC-registered and works within CQC-regulated facilities.