Severity components	Intermittent	Mild persistent asthma	Moderate persistent asthma	Severe persistent asthma
Symptoms	Less than once a week	More than twice per week but not daily	Daily	Throughout the day
Nocturnal symptoms	Less than twice a day per month	Three-four times per month	More than once a week but not every night	Often every night per week
Interference with activity	Brief exacerbations	Exacerbations may cause minor limitation of activity and sleep	Exacerbations more than twice a week and may cause some limitation of activity and sleep	Frequent exacerbations with marked limitation of physical activity
SABA use	</=2 days per week	>2 days per week but not daily and not more than once on any day	Daily	Several times per day
Pulmonary function test	Normal FEV1 between exacerbations	FEV1 > 80% predicted	FEV1 > 60% but < 80% predicted	FEV1 < 60% predicted
	FEV1 > 80% predicted	FEV1/PVC: normal	FEV1/PVC: reduced 5%	FEV1/PVC: reduced 5%
	FEV1/PVC: normal