A 9-year-old boy with suspected asthma undergoes spirometry. Baseline FEV1 is 62% predicted. After administering 400 mcg of salbutamol via MDI, FEV1 improves to 76% predicted. What is the minimum degree of improvement in FEV1 required to demonstrate significant bronchodilator reversibility supporting an asthma diagnosis?

• A FEV1/FVC ratio returning above 0.85
• B Increase of 20% or more from baseline
• C Absolute rise of 100 mL or more
• D Increase of 12% or more from baseline ✓

Explanation

Significant bronchodilator reversibility in children is defined as an increase in FEV1 of 12% or more from baseline (and at least 200 mL in older subjects) after a bronchodilator. This boy improved 14 percentage points, confirming reversibility. The commonly quoted 20% figure applies to variability in peak expiratory flow monitoring over time, not post-bronchodilator spirometry, making option B the tempting distractor.

Reference: Nelson Textbook of Pediatrics, 21st ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.