Asthma-COPD overlap - a discordance between patient populations defined by different diagnostic criteria

Background The concordance between asthma-chronic obstructive pulmonary disease overlap (ACO) defined according to Global Inititative for Asthma (GINA)/Global Initiative for Chronic Obstructive Lung Disease (GOLD) and other diagnostic criteria is unknown. Objective To assess the concordance between different ACO definitions and to estimate the definition-based ACO prevalence and characteristics. Methods A prospective, real-life study based on a 32-item data set was performed in a mixed population of patients with asthma and chronic obstructive pulmonary disease (COPD). Five different definitions of ACO, including the GINA/GOLD criteria, were analyzed. Results A total of 1609 patients were included in the final analysis. Application of Venn diagram for ACO populations resulted in 31 ACO subpopulations, which were further reduced to 6 separate populations by introducing a rank order for the analyzed definitions to classify patients from intersecting groups. Overall, the level of agreement between different ACO definitions was poor. Cohen kappa coefficient for the agreement between ACO GINA/GOLD definition and other ACO definitions varied from 0.06 to 0.21. Only 2 patients (0.12%) met all the ACO definitions. Definition-based ACO prevalence ranged between 3.8% (Spanish criteria) and 18.4% (clinician's diagnosis). A total of 573 (33.4%) patients met the criteria from at least 1 ACO definition. Patients who could not be classified as suffering from “pure” asthma, “pure” COPD, or ACO accounted for as much as 27.5% of the whole investigated group. The most severe symptoms were observed in patients with ACO defined as COPD and asthma diagnosed at age less than 40 years. Conclusions The current ACO definitions identify distinct populations that share only a small number of common features and present with different disease phenotypes. ACO prevalence is highly variable, depending on the definition applied.