Table 1.
Clinical features that when present suggest the diagnosis of asthma or COPD
| Asthma | COPD | ACOS | More compatible with asthma | More compatible with COPD | |
|---|---|---|---|---|---|
| Age of onset | Usually at childhood, but can present at any age | Usually age ≥40 years | Usually age ≥40 years, but onset of symptoms may have been in childhood or early adulthood | • Onset before age 20 years | • Onset after age 40 years |
| Pattern of symptoms | May vary from day to day; often triggered by either non-specific stimuli such as exercise and laughter, or exposure specific inhaled allergens | Chronic usually continuous symptoms, particularly during exercise | Chronic respiratory symptoms including exertional dyspnea are present, but variability of symptoms may be prominent | • Variation in symptoms over minutes, hours, or days • Symptoms worse during night or early morning • Symptoms triggered by exercise, emotions including laughter, dust or exposure to allergens |
• Persistence of symptoms despite treatment • Good and bad days but always symptoms and exertional dyspnea • Chronic cough and sputum preceded onset of dyspnea, unrelated to triggers |
| Lung function • Persistence of airflow Obstruction • Variability of lung function • Course of lung function over time |
• Lung function may be normal between symptoms • Current and/or historical variability of airflow obstruction, bronchodilator reversibility, BHR • Often improves with treatment and remains stable over time, but fixed airflow obstruction can develop in a subset of asthmatics |
• Persistent airflow obstruction • Airflow obstruction may improve to some extent, but airflow obstruction defined as either post-bronchodilator FEV1/FVC <0.7 or LLN persists • Generally slowly progressive over years despite treatment |
• Persistent airflow obstruction • Airflow obstruction is not fully reversible, but often with current or historical bronchodilator reversibility, and/or BHR • Generally slowly progressive decline over years, but to lesser extent than in COPD alone |
• Record of variable airflow obstruction documented with spirometry or peak flow • Lung function normal between symptoms • No worsening of symptoms over time • May improve spontaneously or after treatment with a bronchodilator or ICS |
• Record of persistent airflow limitation • Persistent airflow limitation • Symptoms slowly worsening over time • R apid-acting bronchodilator treatment provides only limited relief |
| Past history or family history of asthma | Many patients have a history of allergy and asthma in childhood and/or a family history of asthma | History of exposure to noxious particles and gases (mainly tobacco smoke and biomass fuels) | Frequently a history of allergy and asthma in childhood and/or a family history of asthma, and/or exposure to noxious particles and gases (mainly tobacco smoke and biomass fuels) | • Previous doctor’s diagnosis of asthma • Family history of asthma and allergy |
• Previous doctor’s diagnosis of COPD or emphysema • History of exposure to noxious particles and gases (mainly tobacco smoke and biomass fuels) |
| Chest X-ray Exacerbations | Usually normal Exacerbations occur, but can be considerably reduced by treatment |
Often shows hyperinflation Exacerbations occur and are often related to co-morbidities. Exacerbation frequency can be reduced by treatment |
Often shows hyperinflation Exacerbations occur more frequently than in asthma or COPD alone, but are reduced by treatment. Co-morbidities can also contribute to exacerbations |
• Normal | • Shows hyperinflation |
| Type of airway inflammation | Characterized by increased numbers of eosinophils in blood, sputum, and bronchial biopsies | Characterized mainly by neutrophils in sputum lymphocytes in bronchial biopsies | Elevated numbers of eosinophils and/or neutrophils can be present in sputum |
Note: When a patient displays clinical features of both diseases, the diagnosis of ACOS is considered.
Abbreviations: COPD, chronic obstructive pulmonary disease; ICS, inhaled corticosteroids; ACOS, asthma–COPD overlap syndrome; FEV1, forced expiratory volume in the first second; FVC, forced vital capacity; BHR, bronchial hyperresponsiveness; LLN, lower limit of normal.