Originally published: December 2017

Key learning points

  • Some patients have asthma and COPD simultaneously, known as asthma–COPD overlap (ACO)
  • These patients experience frequent exacerbations, have worse quality of life, a more rapid decline in lung function and higher mortality than either asthma or COPD alone
  • Based on strict criteria, the prevalence is approximately 10% of people with airways disease
  • In patients with a similar number of features of both asthma and COPD, the diagnosis of ACO should be considered

Introduction

Some patients who present with chronic respiratory symptoms, particularly older patients, have a diagnosis and/or features of both asthma and chronic obstructive pulmonary disease (COPD), with airflow limitation that is not completely reversible after bronchodilatation.1–3 Some have an unequivocal history of poorly-controlled asthma that has resulted in fixed airflow obstruction, but which remains asthma. However, a small group of patients have risk factors for and clinical features of both diseases and the concept of an ‘overlap’ syndrome has been proposed.2,4–10

ACO

In 2015, both the Global Initiative for Chronic Obstructive Lung Disease (GOLD) and Global Initiative for Asthma (GINA) reports included a section discussing the diagnosis and management of the so-called asthma–COPD overlap syndrome (ACOS). In the 2017 reports, the ‘S’ was dropped to emphasise the fact that a new separate disease was not being defined, rather that there is a group of patients who have both asthma and COPD simultaneously, that is, asthma–COPD overlap (ACO).11,12

Patients with ACO experience frequent exacerbations, have worse quality of life, a more rapid decline in lung function and higher mortality than either asthma or COPD alone.2,13 In addition, they consume a disproportionate amount of healthcare resources.14

The true prevalence of ACO is difficult to determine as different studies have used different diagnostic criteria. Some have used very loose definitions and claim prevalence of approximately 25–60% in people with asthma15 or COPD.16 However, using a more realistic definition, including people with clinical features of both asthma and COPD, exposure to a risk factor for COPD and where a firm diagnosis of asthma or COPD cannot be made, the prevalence is around 10–20% of people with airways disease.17,18

A firm diagnosis of asthma or COPD can be made in most patients on the basis of the history and examination and any relevant investigations. GOLD and GINA recommend identifying the features suggestive of a diagnosis of asthma or COPD. If there are three or more of the features listed for either asthma or COPD, and in the absence of those for the alternative diagnosis, there is a strong likelihood of a correct diagnosis of asthma or of COPD (see Table 1).11

Table 1. Syndromic diagnosis of airways disease: features that if present favour asthma or COPD11

FeatureMore likely to be asthma if several of ...*More likely to be COPD if several of ...*
*Syndromic diagnosis of airways disease
Shaded columns list features that when present best identify patients with typical asthma and typical COPD. For a patient, count the number of check boxes in each column. If three or more boxes are checked for asthma or COPD, the patient is likely to have that disease. If there are similar numbers of checked boxes in each column, this is described as asthma-COPD overlap.
Age of onset
  • Onset before age 20 years
  • Onset after age 40 years
Pattern of respiratory symptoms
  • Variation in symptoms over minutes, hours or days
  • Symptoms worse during the night or early morning
  • Symptoms triggered by exercise, emotions including laughter, dust or allergen exposure
  • Persistence of symptoms despite treatment
  • Good and bad days but always daily symptoms and exertional dyspnoea
  • Chronic cough and sputum preceded onset of dyspnoea, unrelated to triggers
Lung function
  • Record of variable airflow limitation (spirometry, peak flow)
  • Record of persistent airflow limitation (post-bronchodilator FEV1/FVC <0.7)
Lung function between symptoms
  • Lung function normal between symptoms
  • Lung function abnormal between symptoms
Past history or family history
  • Previous doctor diagnosis of asthma
  • Family history of asthma and other allergic conditions (allergic rhinitis or eczema)
  • Previous doctor diagnosis of COPD, chronic bronchitis or emphysema
  • Heavy exposure to a risk factor: tobacco smoke, biomass fuels
Time course
  • No worsening of symptoms over time. Symptoms vary either seasonally or from year to year
  • May improve spontaneously or have an immediate response to BD or ICS over weeks
  • Symptoms slowly worsening over time (progressive course over years)
  • Rapid acting bronchodilator treatment provides only limited relief
Chest x-ray
  • Normal
  • Severe hyperinflation

Spirometry confirms chronic airflow limitation but it is of almost no value in distinguishing between asthma with fixed airflow obstruction, COPD and ACO, even taking into account pre- and post-bronchodilator values. Some people with asthma have no or minimal response to short-acting bronchodilators,19 whilst some people with COPD show a large response.20

If a patient has similar numbers of features of both asthma and COPD, the diagnosis of ACO should be considered; however, there is no single diagnostic test or pathognomonic features to confirm the diagnosis.

Management approach

A trial of treatments should be based on the likely diagnosis and where there is still significant doubt, a safety first approach should be adopted and treatment for asthma should be offered. In people with asthma even seemingly ‘mild’ symptoms (compared with those of moderate or severe COPD) might indicate significant risk of a life-threatening attack.4,11 If ACO appears the likely diagnosis, it is recommended that the initial treatment should be based on asthma guidelines with low- or moderate-dose inhaled corticosteroid (ICS) and a long-acting beta-agonists (LABA) or long-acting muscarinic antagonists (LAMA) to be prescribed (ICS + LAMA is an unlicensed indication).4,11

If a patient has persistent symptoms and/or exacerbations despite treatment or if there are clinical features to suggest an alternative diagnosis such as bronchiectasis, pulmonary fibrosis, pulmonary hypertension or cardiovascular diseases, they should be referred for further evaluation.11

Our understanding of ACO is at a very preliminary stage and most studies of asthma and COPD management have had entry criteria that exclude people with ACO. There is an obvious need for more research on ACO.

Professor David Halpin is consultant physician at the Royal Devon and Exeter Hospital and a member of the GOLD Board of Directors and Science Committee.

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