Table 4.

Categorisation of COPD severity by different guidelines

	% of predicted FEV1*
Airflow obstruction	BTS	ATS-ERS	GOLD
Mild	50-80%	≥80%	≥80%
Moderate	30-49%	50-80%	30-79%
Severe	<30%	30-50%	<30%
Very severe		<30%

BTS = British Thoracic Society. ATS-ERS = American Thoracic Society and European Respiratory Society. GOLD = Global Initiative for Chronic Obstructive Lung Disease. The ATS/ERS guidelines also suggest an “at risk” group—smokers with typical symptoms of COPD with an FEV₁/FVC ratio >0.7 and FEV₁ ≥80% predicted. The GOLD guidelines suggest an “at risk” category in smokers with typical symptoms of COPD but normal spirometry

^*FEV₁/FVC ratio should be <0.7 in all cases.