Table 1.

Classification of Asthma⁴

Components of Severity		Asthma Severity
		Intermittent	Persistent
			Mild	Moderate	Severe
Impairment	Symptoms	≤ 2 days per week	> 2 days per week, but not daily	Daily	Throughout the day
	Nighttime awakenings	≤ 2 times per month	3–4 times per month	More than once per week, but not nightly	Often; 7 times per week
	Short-acting beta agonist use for symptom control	≤ 2 days per week	> 2 days per week, but not more than once per day	Daily	Several times per day
	Interference with normal activity	None	Minor limitation	Some limitation	Extreme limitation
	Lung function*	FEV1 > 80% predicted FEV1/FVC normal Normal FEV1 between exacerbations	FEV1 ≥ 80% predicted FEV1/FVC normal	FEV1 > 60% but < 80% predicted FEV1/FVC reduced by up to 5%	FEV1 < 60% predicted FEV1/FVC reduced by more than 5%
Risk	Exacerbations requiring oral systemic corticosteroids	0–1 per year	2 or more per year

FEV₁ = forced expiratory volume in one second; FVC = forced vital capacity.

^*Normal FEV₁/FVC ratio for ages 8–19 years = 85%; ages 20–39 years = 80%; ages 40–59 years = 75%; ages 60–80 years = 70%.