The Asthma-COPD Overlap Syndrome

Posted by • September 25th, 2015

Asthma-COPD Overlap Syndrome 1Although in textbooks asthma and chronic obstructive pulmonary disease (COPD) are viewed as distinct disorders, there is increasing awareness that many patients have features of both. A new review article covers the asthma–COPD overlap syndrome.

Approximately 1 in 12 people worldwide are affected by asthma or chronic obstructive pulmonary disease (COPD); once regarded as two distinct disease entities, these two conditions are now recognized as heterogeneous and often overlapping. The term “asthma-COPD overlap syndrome” (ACOS) has been applied when a person has clinical features of both asthma and COPD.

Clinical Pearls

• Does ACOS have a specific definition?

Even though overlaps between asthma and COPD are a clinical reality, Global Initiative for Asthma (GINA) and Global Initiative for Chronic Obstructive Lung Disease (GOLD) documents have not given a specific definition of ACOS and have stated that more evidence on “clinical phenotypes and underlying mechanisms” is needed.

Table 1. Four Examples of Patients with Obstructive Airway Disease.

• How prevalent is the overlap syndrome, and how is it treated?

According to a case definition of ACOS that has been widely promulgated, the syndrome is estimated to be present in 15 to 45% of  the population with obstructive airway disease, and the prevalence increases with age. However, despite this presumed high prevalence, no double-blind, prospective studies have been conducted to provide information on how to treat these types of patients. Indeed, studies of COPD have excluded nonsmokers and patients with some bronchodilator reversibility, whereas studies of asthma have excluded smokers and patients without substantial ronchodilator reversibility. Thus, the most effective treatment of patients with ACOS remains unknown.

Morning Report Questions

Q: What are some of the features that have traditionally been associated with either asthma or COPD, but can, in fact, be present in both conditions?

A: Reversibility of airway obstruction after inhalation of a bronchodilator drug such as albuterol is a hallmark in early asthma and has long been regarded as a criterion to distinguish asthma from COPD. Reversibility of airway obstruction is frequently present in COPD as well; in two studies, reversibility was observed in up to 44% and 50% of patients with COPD. There is broad consensus that asthma typically has an eosinophilic and a Th2-driven cytokine pattern of inflammation, whereas neutrophilic inflammation dominates in COPD. Bronchial-biopsy studies, sputum studies, and exhaled-breath studies have provided evidence of substantial heterogeneity in mucosal inflammation. Patients with asthma who have severe or late-onset disease or chronic infections or who smoke may also exhibit neutrophilic inflammation and CD8 cells in the airways, both of which were once believed to be hallmarks of COPD. A Th2 inflammatory signature can also be present in COPD. Eosinophils are present in 15 to 40% of patients with stable COPD — in sputum, bronchoalveolar lavage, and lung tissue — even after careful exclusion of patients with reversibility of airway obstruction, bronchial hyperresponsiveness, atopy, or a childhood history of asthma; eosinophil activation is associated with disease severity. Eosinophil levels can also be increased in the sputum of patients with COPD exacerbations.

Figure 2. Risk Factors for Asthma and COPD and the Influence of Environment and Aging.

Q: Should ACOS be designated a disease entity?

A: According to the authors of this review article, it is premature to recommend the designation of ACOS as a disease entity in primary and specialist care. More research is needed to better characterize patients and to obtain a standardized definition of ACOS that is based on markers that best predict treatment response in individual patients. The danger of seeing ACOS as a disease entity is that the lines may be blurred between asthma and COPD, because studies addressing the patient population with ACOS specifically are lacking, which could lead to overtreatment, particularly with inhaled glucocorticoids.

One Response to “The Asthma-COPD Overlap Syndrome”

  1. Abdiaziz says:

    I strongly agree with the authors and as practioner I came across the scenario of Acos but wasn’t sure since we are textbook guided physicians most of the time. But I do agree Acos is a single entity disease from my clinical judgement. Thank you for the update