American Board of Internal Medicine (ABIM) Certification Practice Exam

What is the minimum percentage increase in FEV1 required to confirm reversible airway obstruction in asthma diagnosis?

1. 5%

2. 10%

3. 12%

4. 15%

The correct answer is: 12%

In the context of diagnosing reversible airway obstruction in asthma, a minimum increase of 12% in FEV1 (forced expiratory volume in one second) following the administration of a bronchodilator is generally accepted as indicative of significant reversibility. This threshold is based on clinical studies that demonstrate this percentage reliably indicates a notable improvement in lung function, which is characteristic of asthma. The rationale behind using a 12% increase is that it strikes a balance between sensitivity and specificity for detecting reversibility. A smaller percentage, such as 5% or even 10%, might not adequately represent a meaningful clinical response due to variability in measurement and the influence of other factors like technique, timing, and patient effort. A threshold higher than 12%, such as 15%, while often used in some contexts, is not the standardized criterion for diagnosing asthma, making 12% the minimum recognized threshold for confirming reversible obstruction.