In children older than 5 years, what spirometry criterion indicates a positive bronchodilator response?

• A. An increase in FEV1 of ≥12%.
• B. An increase in FVC of ≥12%.
• C. A decrease in FEV1 of ≥10%.
• D. No change in FEV1.

Answer: (A)

The test is looking at how much a child’s airways improve after using a bronchodilator, measured by spirometry. When you give a bronchodilator, a healthy reversible response shows as a noticeable rise in the amount of air expelled in the first second (FEV1). In children older than five, a positive bronchodilator response is defined as an increase in FEV1 of at least 12% from the baseline value after inhaled bronchodilator therapy. This percentage accounts for normal testing variability and ensures the change reflects true airway improvement rather than measurement noise. FEV1 is the most sensitive measure of reversible obstruction because bronchodilators mainly affect airway caliber, whereas changes in FVC are less specific for reversibility. A decrease in FEV1 or no change after bronchodilator therapy would not indicate reversibility.