In pulmonary function testing for asthma assessment, which result indicates reversible airway disease?

• A. An increase of 12% or more in FEV1 after bronchodilator
• B. A decrease in FEV1 after bronchodilator
• C. No change in FEV1 after bronchodilator
• D. A 50% increase in FEV1 without bronchodilator

Answer: (A)

Reversibility of airway obstruction after bronchodilator is what indicates asthma in pulmonary function testing. FEV1 is the amount of air you force out in one second, and a true reversible obstruction will show a meaningful rise after a bronchodilator is given. The commonly used threshold is an increase of 12% or more in FEV1, usually with an absolute gain around 200 mL in adults, which shows the airwaysRespond to medication and are not permanently narrowed—classically seen in asthma.

If FEV1 decreases after bronchodilator, or if there is no meaningful change, this argues against reversible airway disease and suggests non-reversible obstruction or another pattern. A large increase in FEV1 without bronchodilator isn’t a test of reversibility, since reversibility is assessed specifically with the bronchodilator challenge.