Ongoing lung function testing
Lung function tests should be repeated at regular intervals in patients with asthma. Findings that support the continued diagnosis of asthma include:
- an increase in FEV1 of at least 200 mL and 12% from baseline after a trial of inhaled corticosteroids for 4 weeks
- clinically important variation in lung function between repeat measurements (a change of 20% or more in FEV1 or peak expiratory flow)
- diurnal variation in PEF readings of greater than 10%1
- positive bronchial provocation challenge or exercise challenge in a respiratory function laboratory (only required if the diagnosis is uncertain).