A 28-year-old woman with a 6-month history of intermittent dyspnea, nocturnal cough, wheezing, and chest tightness triggered by exercise, cold air, and allergen exposure presents for spirometry. Pre-bronchodilator (BD) FEV1 is 2.10 L (68% predicted) with FEV1/FVC 0.65. After 400 mcg salbutamol via spacer, post-BD FEV1 increases to 2.62 L (85% predicted), representing a 520 mL (24.8%) increase from baseline. The post-BD FEV1/FVC ratio normalizes to 0.72. The flow-volume loop shows resolution of the pre-BD scooped expiratory limb.

The spirometric pattern marked **A** in the diagram—post-BD FEV1 increase ≥12% AND ≥200 mL from baseline—is the hallmark of which diagnosis?

Question

A 28-year-old woman with a 6-month history of intermittent dyspnea, nocturnal cough, wheezing, and chest tightness triggered by exercise, cold air, and allergen exposure presents for spirometry. Pre-bronchodilator (BD) FEV1 is 2.10 L (68% predicted) with FEV1/FVC 0.65. After 400 mcg salbutamol via spacer, post-BD FEV1 increases to 2.62 L (85% predicted), representing a 520 mL (24.8%) increase from baseline. The post-BD FEV1/FVC ratio normalizes to 0.72. The flow-volume loop shows resolution of the pre-BD scooped expiratory limb.

The spirometric pattern marked **A** in the diagram—post-BD FEV1 increase ≥12% AND ≥200 mL from baseline—is the hallmark of which diagnosis?

Accepted Answer

D. Asthma with significant bronchodilator reversibility. ## Why "Asthma with significant bronchodilator reversibility" is right

The pattern marked **A**—post-BD FEV1 increase ≥12% AND ≥200 mL from baseline—is the diagnostic hallmark of asthma according to ATS/ERS and GINA 2024 guidelines. This patient's 24.8% and 520 mL increase far exceeds these thresholds, confirming reversible airflow obstruction. The normalization of FEV1/FVC ratio post-BD (from 0.65 to 0.72) and restoration of the normal convex expiratory flow-volume curve further support asthma. Combined with her characteristic symptoms (variable dyspnea, wheeze, nocturnal cough, exercise-triggered), atopic history (allergic rhinitis, atopic dermatitis, family history of asthma), elevated FeNO (55 ppb), elevated IgE, and eosinophilia, the diagnosis of asthma is confirmed. GINA 2024 and Harrison's Chapter 287 emphasize that asthma is defined by variable airflow obstruction that is reversible, distinguishing it from fixed obstruction in COPD.

## Why each distractor is wrong

- **COPD with partial response to bronchodilators**: COPD is characterized by FIXED airflow obstruction; post-BD FEV1/FVC remains <0.70 and FEV1 increase is typically <12% or <200 mL. This patient's post-BD FEV1/FVC normalized to 0.72 and showed 24.8% improvement—incompatible with COPD diagnosis.
- **Asthma-COPD overlap syndrome**: While ACO exists, it requires features of both asthma AND COPD (e.g., significant smoking history, persistent airflow obstruction post-BD). This young, non-smoking woman with complete reversibility and normal post-BD spirometry does not meet ACO criteria.
- **Restrictive lung disease with air trapping**: Restrictive disease shows reduced FVC and TLC with normal or elevated FEV1/FVC ratio. This patient has reduced FEV1/FVC (0.65 pre-BD), indicating obstruction, not restriction. Restrictive disease does not show bronchodilator reversibility of this magnitude.

**High-Yield:** Asthma = reversible airflow obstruction (post-BD FEV1 increase ≥12% AND ≥200 mL); COPD = fixed airflow obstruction (post-BD FEV1/FVC remains <0.70). This distinction is fundamental to diagnosis and management.

[cite: GINA 2024 Strategy Report; Harrison's Principles of Internal Medicine, 21st ed., Chapter 287: Asthma]

Answer

A. Restrictive lung disease with air trapping

Answer

B. COPD with partial response to bronchodilators

Answer

C. Asthma-COPD overlap syndrome

Explanation

Why "Asthma with significant bronchodilator reversibility" is right

Why each distractor is wrong

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