The prevalence of asthma-chronic obstructive pulmonary disease overlap (ACO) is highly variable and depends on the definition used, according to study results published in the Journal of Allergy and Clinical Immunology: In Practice.

The current definitions in use identify diverse populations that share only a few features, thus demonstrating that patients with ACO are a heterogeneous group with different phenotypes requiring different therapeutic approaches.

In this prospective multicenter cross-sectional real-life study, investigators sought to evaluate the concordance between different definitions of ACO and estimate the prevalence and characteristics of ACO according to the definition being used. A total of 5 definitions were analyzed, all of which differ in terms of diagnostic criteria. The 5 definitions included the Global Initiative for Asthma and Global Initiative for Chronic Obstructive Pulmonary Disease (GINA/GOLD) criteria, Spanish criteria proposed by Soler-Cataluña and colleagues, current diagnosis of COPD in a patient with asthma who was diagnosed before age 40 (COPD + asthma <40 years), definition proposed by Gibson (Gibson’s criteria), and physician’s diagnosis based on their own experience or beliefs (clinician’s diagnosis). This study, which was based on a 32-item dataset, was performed in a mixed population of patients with asthma and COPD.

Overall, 1609 patients were included in the final analysis. The use of nonproportional Venn diagrams for ACO populations yielded 31 different ACO subpopulations and their mutual intersections, which were reduced further to 6 separate populations. The level of agreement between the different ACO definitions was considered poor. Per Cohen’s kappa coefficient, the level of agreement between ACO GINA/GOLD definitions and other ACO definitions varied between 0.06 and 0.21.


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Only 0.12% (2 of 1609) of the patients fulfilled all the ACO definitions. The definition-based ACO prevalence varied between 3.8% (per Spanish criteria) and 18.4% (per clinician’s diagnosis). Overall, 33.4% of the participants met all of the criteria of ≥1 ACO definition, whereas patients with “pure” asthma and “pure” COPD comprised 7.3% and 20.1% of the group, respectively. Moreover, disease could not be identified as ACO, “pure” asthma, “pure” COPD, chronic bronchitis, or emphysema in 27.7% of participants. The most severe symptoms were reported in patients with ACO in the COPD + asthma <40 years group.

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The investigators concluded that the current definitions of ACO identify distinct populations of patients who share only a small number of characteristics and who present with different disease phenotypes, thus showing that the prevalence of ACO is highly variable and based on the definition applied. The lack of a uniform, widely used definition of ACO affects the estimation of the true burden of this condition, thus impeding the establishment of appropriate management strategies for individual patients.

Disclosures: Several authors report financial relationships with pharmaceutical companies. For a full list of disclosures, please see the original reference.

Reference

Barczyk A, Maskey-Warzęchowska M, Górska K, et al. Asthma-COPD overlap – a discordance between patient populations defined by different diagnostic criteria. J Allergy Clin Immunol Pract.  doi:10.1016/j.jaip.2019.04.022