Bronchodilator Reversibility Calculator
Bronchodilator Reversibility Calculator
The 2022 ERS/ATS standard moved the definition of a bronchodilator response from a percentage of baseline to a percentage of predicted. Both criteria are computed here, with a case where they disagree.
Bronchodilator reversibility
2022 standard and the retired criterionPre 2.00 L, post 2.40 L, predicted 3.32 L — Box 1 of the 2022 standard
Both criteria
Pre-2022: rise of at least 12% of the pre-bronchodilator value AND more than 200 mL
- the 2022 criterion
- quoted from the ERS/ATS technical standard on interpretive strategies: “it is recommended that BDR be classified as a change of >10% relative to the predicted value for FEV1 or FVC”. The standard warns that this is not the same as a 10% change between the pre- and post-bronchodilator values
- the criterion it replaced
- the same document states the 2005 rule as “>200 mL AND ≥12% increase in FEV1 and/or FVC”, and concludes that “the use of approaches 1) and 2) to define BDR are no longer recommended”. Note the asymmetry in the published wording — the volume is strictly greater than 200 mL, the percentage is 12% or more
- why it changed
- the standard’s own reason: “the absolute and relative changes in FEV1 and FVC are inversely proportional to baseline lung function”, and are “associated with height, age and sex in both health and disease”. A rule divided by baseline is easier to pass the worse the baseline is; a rule divided by predicted is not
- FEV1 or FVC
- both criteria are satisfied by a change in either index, and in severe obstruction the FVC response is often the larger
Worked example
Pre 2.00 L, post 2.40 L, predicted 3.32 L — Box 1 of the 2022 standard
Change = 2.40 − 2.00 = 0.40 L = 400 mL
2022 criterion: 100 × 0.40 ÷ 3.32 = 12.05% of predicted, greater than 10%, so the criterion is met
Box 1 reports this case as “an increase of 12.1% of their predicted FEV1”. Recomputing 0.40 ÷ 3.32 gives 12.05%, so the published figure is rounded differently rather than computed differently — stated because a reader checking this page against the standard will see both numbers
Pre-2022 criterion: 0.40 ÷ 2.00 = 20.0% of baseline and 400 mL, so it is met too — on Box 1's own numbers the two criteria agree
Now the baseline dependence, computed rather than asserted. Take a fixed 200 mL rise. At a baseline of 1.00 L it is 20% of baseline and passes the 12% component. At a baseline of 2.00 L the identical 200 mL rise is 10% of baseline and fails it. Same lungs' worth of change, same patient's predicted value, opposite verdicts on that component — decided entirely by where the baseline started. The 2022 criterion, which divides by a predicted value that does not move, calls both cases the same: 6.0% of predicted either way
A detail in the old wording. The 2022 standard prints the retired criterion as greater than 200 mL and at least 12% — strict on the volume, inclusive on the percentage — so a rise of exactly 200 mL does not meet it as written. Many secondary sources render the volume as 200 mL or more; this page follows the standard
A case where the two criteria disagree, old yes and new no. Pre 1.00 L, post 1.25 L, predicted 3.32 L. Old: 25.0% of baseline and 250 mL — met. New: 0.25 ÷ 3.32 = 7.5% of predicted — not met
And the other way, new yes and old no. Pre 3.20 L, post 3.55 L, predicted 3.32 L. New: 0.35 ÷ 3.32 = 10.5% of predicted — met. Old: 0.35 ÷ 3.20 = 10.9% of baseline, below 12% — not met
Neither result names a disease. Both asthma and COPD can be reversible and neither is defined by it
The two criteria, and the wording each comes from
| Criterion | Published wording | On the default inputs |
|---|---|---|
| ERS/ATS 2022 | a change of greater than 10% relative to the predicted value for FEV1 or FVC | 12.0% of predicted — met |
| ATS/ERS 2005, no longer recommended | greater than 200 mL AND at least a 12% increase in FEV1 and/or FVC from baseline | 20.0% of baseline and 400 mL — met |
Where the two criteria disagree, and why
| Pre | Post | Predicted | Change | Percent of baseline | Percent of predicted | Pre-2022 verdict | 2022 verdict |
|---|---|---|---|---|---|---|---|
| 1.00 L | 1.25 L | 3.32 L | 250 mL | 25.0% | 7.5% | Met | Not met |
| 1.00 L | 1.20 L | 3.32 L | 200 mL | 20.0% | 6.0% | Not met | Not met |
| 2.00 L | 2.20 L | 3.32 L | 200 mL | 10.0% | 6.0% | Not met | Not met |
| 3.20 L | 3.55 L | 3.32 L | 350 mL | 10.9% | 10.5% | Not met | Met |
| 2.00 L | 2.40 L | 3.32 L | 400 mL | 20.0% | 12.0% | Met | Met |
What changed in 2022, and why the baseline was the problem
For seventeen years a bronchodilator response meant a rise in FEV1 or FVC of at least 12% of the pre-bronchodilator value and more than 200 mL. The 2022 ERS/ATS technical standard retired that rule and replaced it with a change greater than 10% of the predicted value. The reason is stated in the document itself: the absolute and relative changes in FEV1 and FVC “are inversely proportional to baseline lung function”, and are associated with height, age and sex in health as well as in disease.
That is worth stating concretely, because it is the whole argument. A 200 mL rise is 20% of a 1.00 L baseline and 10% of a 2.00 L baseline, so the old criterion became easier to satisfy the worse the starting FEV1 was — the patients most likely to be called reversible were those with the least lung function left, for an arithmetic reason unconnected to airway smooth muscle. Dividing by the predicted value removes it, because the predicted value does not move when the disease does.
Two consequences follow, in opposite directions. Patients with severe obstruction become harder to call reversible, because a modest absolute change is a small share of their predicted value even though it is a large share of their baseline. Patients with a near-normal baseline become easier. The calculator prints both criteria side by side so a reader comparing a current report with an older one can see which rule produced which word.
What neither criterion does is name a disease. The standard is explicit that bronchodilator responsiveness “does not accurately differentiate between types of airway diseases” and should not be used to make diagnostic decisions. Asthma can be irreversible on the day it is tested; COPD is frequently reversible by either criterion; and a negative test excludes neither. Predicted values, lower limits of normal and z-scores are reference-set dependent: GLI 2012, the race-neutral GLI Global average equations, NHANES III and the older ECSC equations give different predicted values for the same person, and a result can cross a threshold purely because the laboratory changed reference set. Read this against the set printed on your own report. This supports a clinician’s judgement rather than replacing it.
Frequently asked questions
What is the current definition of bronchodilator reversibility?
A change greater than 10% of the predicted value for FEV1 or FVC, from the 2022 ERS/ATS technical standard on interpretive strategies for routine lung function tests. The standard warns that this is not the same as a 10% change between the pre- and post-bronchodilator values, which is a different and smaller denominator.
What was wrong with the old 12% and 200 mL rule?
It depended on the baseline. The standard’s own reason is that the absolute and relative changes in FEV1 and FVC “are inversely proportional to baseline lung function”, so the rule was easier to meet the worse the starting FEV1 was. An identical 200 mL rise is 20% of a 1.00 L baseline and 10% of a 2.00 L baseline — a change of verdict driven by arithmetic rather than by the airway.
Can the old and new criteria disagree?
Yes, in both directions. Pre 1.00 L, post 1.25 L with a predicted of 3.32 L meets the old criterion (25% of baseline, 250 mL) and fails the new one (7.5% of predicted). Pre 3.20 L, post 3.55 L with the same predicted meets the new criterion (10.5% of predicted) and fails the old one (10.9% of baseline, short of 12%).
Does a positive bronchodilator response mean asthma rather than COPD?
No. The 2022 standard states that bronchodilator responsiveness “does not accurately differentiate between types of airway diseases”. Both conditions can be reversible, neither is defined by reversibility, and a negative test on one day does not exclude a variable obstruction.
Should FEV1 or FVC be used?
Either. Both criteria are satisfied by a change in FEV1 or in FVC. In severe obstruction the FVC response is often the larger, because a bronchodilator can extend the usable emptying time before it improves flow, so reporting only FEV1 can miss a real response.
Related calculators
References
- Stanojevic S, Kaminsky DA, Miller MR, et al. ERS/ATS technical standard on interpretive strategies for routine lung function tests. Eur Respir J. 2022;60(1):2101499.
- Global Initiative for Chronic Obstructive Lung Disease. Pocket Guide to COPD Diagnosis, Management and Prevention: 2025 Report. GOLD, 2024.
- BMJ Best Practice. Chronic obstructive pulmonary disease: diagnostic criteria. London: BMJ Publishing Group, 2025.
- Bhakta NR, Bime C, Kaminsky DA, et al. Race and ethnicity in pulmonary function test interpretation: an official American Thoracic Society statement. Am J Respir Crit Care Med. 2023;207(8):978–95.
Not medical advice. For healthcare professionals and education. Reference intervals vary by laboratory and assay — always use your own laboratory's. Never base a dose or a treatment decision on this page alone. Full disclaimer at calcengines.com/disclaimer/