. Author manuscript; available in PMC: 2012 Apr 23.

Published in final edited form as: Eur Respir J. 2009 May 21;34(3):588–597. doi: 10.1183/09031936.00164608

TABLE 2.

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

Threshold for COPD	Formula
Fixed ratio	FEV1/FVC <0.7 (GOLD stage 1 or higher)
LLN (FEV1/FVC)	FEV1/FVC <5th percentile (predicted FEV1/FVC minus 1.645×SD)
GOLD stages 2–4	FEV1/FVC <0.7 and FEV1 <80% pred
LLN (FEV1/FVC) and FEV1 <80% pred	FEV1/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% pred	FEV1/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.