Asthma/Obstructive Pulmonary Disease Overlap

Update on Definition, Biomarkers, and Therapeutics

August Generoso; John Oppenheimer


Curr Opin Allergy Clin Immunol. 2020;20(1):43-47. 

In This Article

Abstract and Introduction


Purpose of review: Asthma/chronic obstructive pulmonary disease overlap (ACO) continues to be a poorly understood condition. This review discusses newly proposed criteria and potential biomarkers in ACO, to aid in diagnosis and research studies, and prudent therapeutic approaches.

Recent findings: A global expert panel proposed an operational definition consisting of major and minor criteria as a step toward defining ACO. Serum periostin and YKL-40 may serve as biomarkers for ACO. Clinically, a reasonable therapeutic approach to ACO is the early addition of a long-acting β-agonist (LABA) and/or a long-acting muscarinic antagonist (LAMA) to an inhaled corticosteroid (ICS).

Summary: Both the proposed criteria and the described biomarkers for ACO can help guide clinicians in identifying this condition as well as aid researchers in designing much needed future studies. In the meantime, clinicians can treat potential ACO patients using the above approach, until therapeutic studies in clearly defined ACO patients are performed.


Patients with persistent airflow obstruction who exhibit features of both asthma and chronic obstructive pulmonary disease (COPD) are categorized into a group called asthma/COPD overlap (ACO).[1,2] To date, ACO continues to be poorly understood as studies of this condition are lacking. This is a consequence of having no clear definition of ACO, hindering the ability of investigators to truly study it; along with clinical trials solely enrolling pure populations of either asthma or COPD patients, excluding those with overlapping features.[3,4] The inclusion of such patients is critical in understanding ACO, as it is uncertain whether ACO represents a distinctly different disorder from asthma and COPD, whether a diagnosis of ACO alters treatment options, and whether disease-related outcomes for ACO differ from asthma-only or COPD-only. Though uncertainty remains, it is argued that ACO is actually a unique entity. Two arguments for this position are that various proposed diagnostic criteria and studies of potential biomarkers distinguish ACO from both asthma and COPD.[4] Moreover, it is also argued that the presence of ACO does affect treatment choices, as is exemplified by the current treatment recommendations set forth by COPD guidelines for patients with COPD symptoms only (treat with LABA only) versus COPD with an asthma component (add ICS). Finally, currently it seems ACO does affect clinical outcomes as it is reported to be associated with more frequent exacerbations, poorer quality of life, more rapid decline in lung function, higher mortality, and greater healthcare utilization compared to asthma or COPD.[4–6] This review will cover the prevalence/natural history, disease mechanism, influencing factors, potential biomarkers, proposed criteria, and therapeutic approaches with regard to ACO.