Which test is most accurate for diagnosing and tracking progression of chronic obstructive pulmonary disease?

• A. Pulmonary function test
• B. Arterial blood gas
• C. Chest radiograph
• D. Maximal exercise test

Answer: (A)

Pulmonary function testing, especially spirometry, directly measures the airflow limitation that defines COPD, making it the most accurate test for both diagnosing the disease and tracking its progression. When performed with a bronchodilator, spirometry provides a post-bronchodilator FEV1/FVC ratio that confirms COPD, and repeating these measurements over time shows how rapidly FEV1 declines, helping to gauge severity and progression (often categorized by GOLD stages).

Arterial blood gas looks at gas exchange and hypoxemia, but it doesn’t diagnose COPD or track its course as reliably. A chest radiograph can reveal structural changes like hyperinflation but is insensitive for detecting early COPD. A maximal exercise test assesses exercise capacity, which is useful for functional status but not the primary method for diagnosing COPD or monitoring its progression.