C3. Assessing the severity of COPD

Airflow limitation, COPD symptoms, and exacerbation risk should be assessed regularly, as they relate to prognosis and can guide COPD management strategies and treatment decisions. Spirometry is the most reproducible, standardised and objective way of measuring airflow limitation, and FEV1 is the variable most strongly associated with prognosis (Peto 1983).

Exacerbations are an important complication of COPD (see X: Manage eXacerbations). The future risk of exacerbations should be assessed in patients with COPD. Exacerbations are more frequent with increased severity of COPD. The most important risk factor for exacerbations is a history of past exacerbations; other factors include gastro-oesophageal reflux, poorer quality of life and elevated white cell count (Hurst 2010). A systematic literature review that included data from 76 studies confirmed that a past history of exacerbations is the most important predictor of future exacerbation risk (Hurst 2022) [evidence level I].

Similar to some other frameworks, the COPD-X Plan proposes classifying disease severity according to symptoms and airflow limitation most typical for each grade. See Box 4 for a summary of the commonly observed FEV₁ range, symptoms and complications for mild, moderate and severe COPD. However, it should be noted that some patients with an FEV1 >80% predicted, although within the normal range, may have airflow limitation (FEV1/FVC ratio <70%).