A patient with suspected obstructive lung disease has spirometry showing FVC 4.0 L, FEV1 2.4 L, and FEV1/FVC 60%. After bronchodilator, FEV1 improves to 2.88 L. What is the % reversibility and does it confirm bronchial asthma?

• A Reversibility 15%; equivocal — does not confirm asthma alone
• B Reversibility 20% with absolute increase of 480 mL — confirms significant reversibility consistent with asthma ✓
• C Reversibility 30%; likely occupational asthma
• D Reversibility 12% — does not meet criteria for significant reversibility

Explanation

Percentage reversibility = (post − pre FEV1) / pre FEV1 × 100 = (2.88 − 2.4) / 2.4 × 100 = 0.48/2.4 × 100 = 20%. Absolute increase = 2.88 − 2.4 = 0.48 L = 480 mL. ATS/ERS criteria for significant reversibility: ≥12% AND ≥200 mL increase from pre-bronchodilator FEV1. This patient meets both criteria (20% and 480 mL), confirming significant bronchodilator reversibility consistent with asthma or reversible component of COPD. COPD patients may show some reversibility, but 20% with 480 mL strongly suggests asthma.

Reference: Guyton & Hall, Textbook of Medical Physiology, 14th ed.

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Written and medically reviewed by the StethoPrep medical team.