A 62-year-old male smoker with a 40 pack-year history presents with progressive dyspnea, chronic cough, and sputum production for 5 years. Clinical examination reveals barrel chest, pursed-lip breathing, and reduced breath sounds bilaterally. Which investigation is most appropriate to confirm the diagnosis and assess the severity of airflow obstruction?

Question

Accepted Answer

B. Spirometry with bronchodilator response. ## Investigation of Choice in COPD Diagnosis

### Why Spirometry with Bronchodilator Response?

**Key Point:** Spirometry is the gold standard investigation for diagnosing and grading the severity of COPD. It objectively measures airflow obstruction and is essential for diagnosis confirmation.

**High-Yield:** The diagnostic criterion for COPD is a post-bronchodilator FEV₁/FVC ratio < 0.70, as per GOLD criteria. This distinguishes COPD from other obstructive diseases and confirms irreversible airflow obstruction.

### Spirometry Parameters in COPD

| Parameter | Finding in COPD | Clinical Significance |
|-----------|-----------------|----------------------|
| FEV₁/FVC ratio | < 0.70 (post-BD) | Diagnostic hallmark |
| FEV₁ | Reduced | Severity grading |
| FVC | Normal or reduced | Emphysema component |
| TLC | Increased | Air trapping |
| RV | Increased | Hyperinflation |

**Clinical Pearl:** Bronchodilator response (BD) testing with a short-acting beta-2 agonist helps distinguish COPD (minimal BD response, <12% and <200 mL improvement) from asthma (significant BD response).

### Severity Classification (GOLD)

1. **GOLD 1 (Mild):** FEV₁ ≥ 80% predicted
2. **GOLD 2 (Moderate):** FEV₁ 50–79% predicted
3. **GOLD 3 (Severe):** FEV₁ 30–49% predicted
4. **GOLD 4 (Very Severe):** FEV₁ < 30% predicted

**Tip:** Always perform spirometry before and after bronchodilator administration to assess reversibility and confirm the diagnosis.

Answer

A. High-resolution computed tomography (HRCT) of the chest

Answer

C. Chest X-ray with inspiratory and expiratory views

Answer

D. Arterial blood gas analysis at rest

Explanation

Investigation of Choice in COPD Diagnosis

Why Spirometry with Bronchodilator Response?

Spirometry Parameters in COPD

Severity Classification (GOLD)

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Parameter	Finding in COPD	Clinical Significance
FEV₁/FVC ratio	< 0.70 (post-BD)	Diagnostic hallmark
FEV₁	Reduced	Severity grading
FVC	Normal or reduced	Emphysema component
TLC	Increased	Air trapping
RV	Increased	Hyperinflation