Table 2—

Previous classification system for asthma severity

Clinical features before treatment#
SymptomsNight-time symptomsLung function
Step 4: severe persistentContinual symptomsFrequentFEV1 or PEF ≤60% pred
Limited physical activityPEF variability >30%
Frequent exacerbations
Step 3: moderate persistentDaily symptomsMore than once per weekFEV1 or PEF >60 and ≤80% pred
Daily use of inhaled SABAPEF variability >30%
Exacerbations affect activity
Exacerbations more than twice per week; may last days
Step 2: mild persistentSymptoms more than twice per week but no more than once per dayMore than twice per monthFEV1 or PEF ≥80% pred
Exacerbations may affect activityPEF variability 20–30%
Step 1: mild intermittentSymptoms no more than twice per weekNo more than twice per monthFEV1 or PEF ≥80% pred
Asymptomatic and normal PEF between exacerbationsPEF variability <20%
Exacerbations are brief (from a few hours to a few days); intensity may vary
  • From the National Asthma Education and Prevention Program Expert Panel Report 2 1. Asthma severity was classified by clinical characteristics before treatment. FEV1: forced expiratory volume in one second; PEF: peak expiratory flow; % pred: % predicted; SABA: short-acting β2-agonist. #: the presence of one of the features of severity is enough to place the patient in that category. An individual should be assigned to the most severe grade in which any feature occurs. The characteristics noted are general and may overlap because asthma is highly variable. Furthermore, an individual’s classification may change over time. : Patients at any level can have mild, moderate or severe exacerbations. Some patients with intermittent asthma experience severe and life-threatening exacerbations separated by long periods of normal lung function and no symptoms.