COPD: investigation and diagnosis
NICE recommend considering a diagnosis of COPD in patients over 35 years of age who are smokers or ex-smokers and have symptoms such as exertional breathlessness, chronic cough or regular sputum production.
The following investigations are recommended in patients with suspected COPD:
The severity of COPD is categorised using the FEV1*:
Measuring peak expiratory flow is of limited value in COPD, as it may underestimate the degree of airflow obstruction.
*note that the grading system has changed following the 2010 NICE guidelines. If the FEV1 is greater than 80% predicted but the post-bronchodilator FEV1/FVC is < 0.7 then this is classified as Stage 1 - mild
**symptoms should be present to diagnose COPD in these patients
The following investigations are recommended in patients with suspected COPD:
- post-bronchodilator spirometry to demonstrate airflow obstruction: FEV1/FVC ratio less than 70%
- chest x-ray: hyperinflation, bullae, flat hemidiaphragm. Also important to exclude lung cancer
- full blood count: exclude secondary polycythaemia
- body mass index (BMI) calculation
The severity of COPD is categorised using the FEV1*:
| Post-bronchodilator FEV1/FVC | FEV1 (of predicted) | Severity |
|---|---|---|
| < 0.7 | > 80% | Stage 1 - Mild** |
| < 0.7 | 50-79% | Stage 2 - Moderate |
| < 0.7 | 30-49% | Stage 3 - Severe |
| < 0.7 | < 30% | Stage 4 - Very severe |
Measuring peak expiratory flow is of limited value in COPD, as it may underestimate the degree of airflow obstruction.
*note that the grading system has changed following the 2010 NICE guidelines. If the FEV1 is greater than 80% predicted but the post-bronchodilator FEV1/FVC is < 0.7 then this is classified as Stage 1 - mild
**symptoms should be present to diagnose COPD in these patients