There is no consensus on the definition and number of different COPD phenotypes, which may be anywhere from two to 328 million (estimated worldwide number of patients with COPD in 2010).8 Some clinically relevant COPD phenotypes include:8
- ‘frequent exacerbators’ with two or more exacerbations per year, who may benefit from anti-inflammatory treatment added to bronchodilators
- ‘overlap COPD-asthma’ who have an enhanced response to inhaled corticosteroids
- ‘infrequent exacerbators’ whose treatment may be based on long-acting bronchodilators, either alone or in combination; and
- high rates of ‘comorbidities’, particularly cardiovascular disease and metabolic syndrome, who may benefit from aggressive risk-factor management (Box 1).
Who is at risk of COPD?
Tobacco smoking remains the major risk factor for COPD. However, even among heavy smokers, fewer than 50% develop clinically significant COPD, and some genuinely light smokers or nonsmokers develop chronic airflow limitation.5 Genetics, lung growth and development, asthma and other environmental exposures are some of the factors that can lead to an individual developing COPD in later life. COPD is generally thought to result from an accelerated decline in FEV1 over time, but in some patients it may be related to reaching early adulthood with a low FEV1 due to impaired lung development during neonatal, childhood or adolescent periods (Figure 1).9
COPD should be considered in any patient who has dyspnoea, chronic cough or sputum production, and a history of exposure to risk factors for the disease, mainly smoking (usually more than 10 to 15 pack years). Measurement of FEV1 by spirometry remains the diagnostic test for COPD and should be performed in all patients with suspected COPD. COPD is defined as a postbronchodilator FEV1 to forced vital capacity (FVC) ratio of below 0.7.10 If the airflow obstruction is fully reversible, the patient should be treated as for asthma.10
Under-recognition and underdiagnosis of COPD remain prevalent. However, patients with a history of smoking and symptoms suggestive of COPD need thorough assessment; the problem may be COPD alone, but often symptoms are due to a combination of cardiovascular disease, deconditioning and other issues, as well as airways disease. There is a continuum of COPD from mild to severe disease. Severity of airflow obstruction and the patient’s symptoms are taken into account. One classification, from the COPD-X guidelines, is shown in Table 1.10
Who is at risk of a COPD exacerbation?
All patients with COPD may develop exacerbations, and even those with underlying mild disease may experience a severe exacerbation, particularly in the winter months. Those with severe COPD are more likely to have a serious outcome even with a mild exacerbation. The single best predictor of exacerbations is previous exacerbations, across all levels of COPD severity. However, exacerbations also become more frequent as COPD severity worsens.