Should the diagnosis of COPD be based on a single spirometry test?

Area of Science:

• Pulmonary Medicine
• Diagnostic Spirometry
• Respiratory Health

Background:

• Clinical guidelines currently recommend a single spirometry test for diagnosing chronic obstructive pulmonary disease (COPD).
• The long-term stability of COPD diagnosis, particularly based on the forced expiratory volume in 1 second over forced vital capacity (FEV1/FVC) ratio, remains underreported.

Purpose of the Study:

• To investigate the diagnostic category shifts (obstructed vs. non-obstructed) in primary care subjects at risk for COPD.
• To assess the stability of COPD diagnosis over time using spirometry in a symptomatic, at-risk population.

Main Methods:

• Utilized data from 2,352 symptomatic individuals (40+ years, ex-smokers) referred for diagnostic spirometry.
• Conducted three spirometry tests for each subject, spaced 12±2 months apart.
• Defined obstruction using both the lower limit of normal (LLN) and a fixed ratio (<0.70) for post-bronchodilator FEV1/FVC.

Main Results:

• At baseline, 32.2% (LLN) and 46.6% (fixed ratio) of subjects were classified as obstructed.
• Within 1-2 years, 14.3% to 15.4% of subjects changed diagnostic category.
• A significant proportion (up to one-third) of initially obstructed patients shifted to a non-obstructed status upon re-testing.

Conclusions:

• A COPD diagnosis based on a single spirometry test may be unreliable due to significant shifts in diagnostic categories over time.
• Repeated spirometry testing is crucial for accurate and stable diagnosis of COPD in symptomatic individuals at risk.
• The findings have implications for patient management and healthcare resource allocation, suggesting a need to re-evaluate current diagnostic criteria.