Classification of asthma severity by clinical features before treatment
Intermittent |
Symptoms less than once a week |
Brief exacerbations |
Nocturnal symptoms not more than twice a month |
FEV1 or PEF ≥80% pred |
PEF or FEV1 variability <20% |
Mild persistent |
Symptoms more than once a week but less than once a day |
Exacerbations may affect activity and sleep |
Nocturnal symptoms more than twice a month |
FEV1 or PEF ≥80% pred |
PEF or FEV1 variability <20–30% |
Moderate persistent |
Symptoms daily |
Exacerbations may affect activity and sleep |
Nocturnal symptoms more than once a week |
Daily use of inhaled short-acting β2-agonist |
FEV1 or PEF 60–80% pred |
PEF or FEV1 variability >30% |
Severe persistent |
Symptoms daily |
Frequent exacerbations |
Frequent nocturnal asthma symptoms |
Limitation of physical activities |
FEV1 or PEF ≤60% pred |
PEF or FEV1 variability >30% |
FEV1: forced expiratory volume in one second; PEF: peak expiratory flow; % pred: % predicted.