Table 2—

Definitions of chronic obstructive pulmonary disease(COPD) used in this analysis

Threshold for COPDFormula
Fixed ratioFEV1/FVC <0.7 (GOLD stage 1 or higher)
LLN (FEV1/FVC)FEV1/FVC <5th percentile (predicted FEV1/FVC minus 1.645×sd)
GOLD stages 24FEV1/FVC <0.7 and FEV1 <80% pred
LLN (FEV1/FVC) and FEV1 <80% predFEV1/FVC <5th percentile and FEV1 <80% pred
LLN (FEV1/FVC) and LLN (FEV1)FEV1/FVC <5th percentile and FEV1 <5th percentile
LLN (FEV1/FEV6) and FEV1 <80% predFEV1/FEV6 <5th percentile and FEV1 <80% pred
  • For all but the fixed ratio, alternative versions may be computed based on choice of prediction equation. This table just describes general formulas. FEV1: forced expiratory volume in 1 s; FVC: forced vital capacity; GOLD: Global Initiative for Chronic Obstructive Lung Disease; LLN: lower limit of normal; % pred: % predicted; FEV6: forced expiratory volume in 6 s.