| Finding | Consistent with | ||
| Asthma | COPD | Asthma–COPD overlap | |
| Normal FEV1/FVC before or after bronchodilator | Yes | No | No * |
Abnormal lung function (post-bronchodilator reduced FEV1/FVC and FEV1 < lower limit of normal) | Yes # | Yes | Yes |
Airflow limitation with greater bronchodilator reversibility than in healthy population (post-bronchodilator FEV1 increase ≥12% and 200 mL from baseline) | Yes ‡ | Yes | Yes |
Marked bronchodilator reversibility (FEV1 increase ≥12% and 400 mL from baseline) | Yes | Possible but unusual † | Possible § |
Additional information
FEV1/FVC: ratio of forced expiratory volume in one second (FEV1) to forced vital capacity (FVC), either before or after bronchodilator
* Normal FEV1/FVC is not consistent with COPD unless there is other evidence of chronic non-reversible expiratory airflow limitation.
# This finding is consistent with asthma that is poorly controlled or measured during a flare-up, or can be seen in some patients with longstanding asthma.
‡ The greater the variation, and the more times variation is seen, the more likely the diagnosis of asthma. However, some patients with longstanding asthma may develop persistent airflow limitation.
† Marked bronchodilator responsiveness strongly favours asthma and is generally inconsistent with COPD, but does not rule out co-existing asthma and COPD.
§ This finding may be seen in patients with co-existing asthma and COPD, or occasionally in COPD, especially when FEV1 is low.