Summary of criteria
| Expiratory airway obstruction | FEV1%(F)VC (corrected for age and gender) |
| No obstruction |
above 5th percentile, and no bronchodilator response |
| Mild obstruction |
below 5th percentile and FEV1 > 60% predicted, or above 5th percentile and bronchodilator response |
| Moderate obstruction |
below 5th percentile and 40% < FEV1 < 60% predicted |
| Severe obstruction |
below 5th percentile and FEV1 < 40% predicted |
| Bronchodilator response | |
| No responsiveness |
Increase in FEV1< 200 mL and < 9% initial FEV1 |
| Mild responsiveness |
Increase in FEV1 > 200 mL and/or > 9% initial FEV1 |
| Marked responsiveness |
Increase in FEV1 > 12% initial FEV1 and > 200 mL |
| Possibly a response |
According to FEV1 no bronchodilator responsiveness, but increase in (F)VC > 340 mL and/or > 12% predicted value and fall in FEV1%(F)VC < 2%: the increase in (F)VC might reflect better subject cooperation. |
| Reversibility of airway obstruction | |
No reversibility |
Airway obstruction but no response to bronchilator drug |
| Partial reversibility |
In spite of the response to a bronchodilator drug the FEV1%(F)VC is still below the 5th percentile |
| Completely reversible |
FEV1%(F)VC after the bronchodilator drug is above the 5th percentile |
| VC too low | |
| Moderate |
below 5th percentile but SDS* > -3 |
| Severe |
SDS* < -3.0 |
| FEV1 | |
Too low |
below 5th percentile |
* SDS = Z-score = standard deviation score