American Board of Internal Medicine (ABIM) Certification Practice Exam

If a patient has an asthma diagnosis confirmed by spirometry, what is the minimal absolute increase in FEV1 that would qualify?

1. 100 mL

2. 200 mL

3. 250 mL

4. 300 mL

The correct answer is: 200 mL

To confirm a diagnosis of asthma using spirometry, a significant increase in FEV1 (forced expiratory volume in one second) after bronchodilator administration is necessary. The minimal absolute increase in FEV1 that is typically accepted to signify a positive response to bronchodilators, indicating reversible airway obstruction consistent with asthma, is at least 200 mL. This threshold is rooted in clinical studies that demonstrate that an increase of this magnitude reflects a meaningful response to bronchodilator therapy and supports the diagnosis of asthma. The significance of identifying at least a 200 mL increase lies in its role as a marker for airflow obstruction that can be improved with treatment, which is a hallmark of asthma. If the increase is less than this value, it may not provide sufficient evidence for the diagnosis and could suggest alternative or more chronic forms of lung disease that do not respond as favorably to bronchodilators. Thus, an increase of 200 mL serves as a practical and clinically relevant threshold, facilitating both the diagnosis of asthma and the decision-making regarding management strategies for the patient.