A 28-year-old woman has episodic cough and nocturnal wheeze. Spirometry shows FEV1/FVC 0.74 with an FEV1 of 2.4 L. After 400 mcg of inhaled salbutamol, FEV1 rises to 2.85 L. Which finding establishes the diagnosis of bronchial asthma?
- A Post-bronchodilator increase in FEV1 of at least 12% and at least 200 mL from baseline ✓
- B FEV1/FVC ratio below 0.70 after bronchodilator
- C Reduction in DLCO below 80% predicted
- D Diurnal peak expiratory flow variation of less than 10%
Correct answer: A. Post-bronchodilator increase in FEV1 of at least 12% and at least 200 mL from baseline
Explanation
Asthma is defined by reversible airflow obstruction: a post-bronchodilator rise in FEV1 of 12% or more AND 200 mL or more confirms significant reversibility and supports asthma. Here the rise is 450 mL (about 18%), meeting the criterion. Option D is wrong because increased variability (not decreased) supports asthma, and option C is wrong because DLCO is normal or raised in asthma, unlike emphysema where it falls.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.