Classification of asthma

Asthma is classified into four categories based upon frequency of symptoms and objective measures, such as peak flow measurements and/or spirometry results. These categories are: mild intermittent; mild persistent; moderate persistent; and severe persistent. Your physician will determine the severity and control of your asthma based on how frequently you have symptoms and on lung function tests. It is important to note that a person’s asthma symptoms can change from one category to another.

Mild intermittent asthma

• Symptoms occur less than two times a week, and nighttime symptoms occur less than two times per month.


• Asthma episodes are brief (a few hours to a few days).


• Lung function tests are greater than 80% of predicted values. Predictions are often made on the basis of age, sex, and height. For a person with asthma, the “predicted” figure could be replaced by the person’s own personal best test value as the figure for comparison.

Mild persistent asthma

• Symptoms occur more than two times per week but not every day.


• Lung function tests are greater than 80% of predicted.

Moderate persistent asthma

• Symptoms occur daily.


• Asthma symptoms affect activity, occur more than two times per week, and may last for days.


• There is a reduction in lung function, with a lung function test range of 60% to 80% of predicted.

Severe persistent asthma

• Symptoms occur continuously, with asthma at night frequently.


• Activities are limited.


• Lung function is decreased to less than 60% of predicted.