Table 1.

Classification of severity of COPD using GOLD criteria (GOLD 2005)

Stage	Characteristic
	FEV1/FVCa	FEV1, % predicteda	Chronic symptomsb
0 (at risk)	Normal	Normal	+
I (mild COPD)	<70%	≥ 80%	±
II (moderate COPD)	<70%	<80% but ≥ 50%	±
III (severe COPD)	<70%	<50% but ≥ 30%	±
IV (very severe COPD)	<70%	<30%; or <50% with chronic respiratory failurec	±

^aClassification based on post-bronchodilator FEV₁.

^bCough, sputum production.

^cArterial partial pressure of oxygen (PaO₂) less than 8.0 kPa (60 mmHg) with or without arterial partial pressure of CO₂ (PaCO₂) greater than 6.7 kPa (50 mmHg) while breathing air at sea level.

Abbreviations: FEV₁, forced expiratory volume in one second; FVC, forced vital capacity.