Mild: FEV1/FVC ratio < 70%, FEV1 ≥ 80% of predicted Moderate: FEV1/FVC ratio < 70%, FEV1 ≥ 50% but < 80% of predicted Severe: FEV1/FVC ratio < 70%, FEV1 < 50% of predicted
FEV1/VC ratio below LLN*
FEV1/FVC ratio ≤ 0.70 and normal, reduced, or increased FEV1 and FVC percent predicted
Restrictive
FEV1/FVC ratio ≥ 70 and FVC < 80% of predicted
TLC below LLN or FEV1/VC ratio ≥ 85 and a reduced VC
FEV1/FVC ratio ≥ 0.75, FEV1 and FVC < 75% of predicted
Mixed
No criteria reported
FEV1/VC ratio and TLC below LLN
FEV1/FVC ratio > 0.70 and < 0.75 and both FEV1 and FVC < 75% predicted
Vital capacity (VC) measures were unavailable, so we used FEV1/FVC ratio instead of FEV1/VC ratio as suggested by 2005 ATS/ERS guidelines.
*Lower limit of normal.