What percentage change in FEV1 after bronchodilator use supports the diagnosis of asthma?

A percentage change of 10% in FEV1 (Forced Expiratory Volume in 1 second) after bronchodilator use is used to support the diagnosis of asthma. This criterion reflects a significant degree of reversibility in airway obstruction, which is a hallmark of asthma.

In individuals with asthma, the airways are often hyperresponsive, and their obstruction can typically be reversed with bronchodilators. A 10% increase in FEV1 indicates that there is some degree of airway reactivity, making it a useful threshold for clinical diagnosis.

Higher thresholds, such as 15% or 20%, may indicate even greater reversibility but are not the standard benchmark for diagnosis. A lower percentage, like 5%, does not provide sufficient evidence of significant airway obstruction reversibility typically seen in asthma. Thus, a 10% increase in FEV1 effectively supports the diagnosis and reflects the characteristic nature of this respiratory condition.