The prevalence of asthma-chronic obstructive pulmonary disease (COPD) overlap (ACO) was similar in cohorts of patients with severe asthma and COPD when identical diagnostic criteria were used, according to study findings published in Therapeutic Advances in Respiratory Disease.
Treating patients with ACO can be challenging because they are typically excluded from research trial focused on either asthma or COPD, and because the definition of ACO can be inconsistent. In addition, these patients have more severe symptoms and worse lung function than those with asthma or COPD alone. In the current study, researchers sought to compare the clinical characteristics of patients with identically-defined ACO from COPD and asthma cohorts.
For COPD data, researchers used the Korean COPD subgroup study (KOCOSS) cohort, which included participants at least 40 years of age who were diagnosed with COPD by a pulmonologist according to chronic respiratory symptoms and spirometry-revealed fixed airflow limitation (post-bronchodilator forced expiratory volume in 1 second [FEV1] to forced vital capacity [FVC] ratio <0.7). The asthma data set, the International Severe Asthma Registry (ISAR) cohort, included adult patients (aged ≥18 years) with severe asthma with Global Initiative for Asthma (GINA) step 5 or uncontrolled asthma at GINA step 4 per the 2018 GINA recommendation.
All study participants included for analysis were at least 40 years of age who had post-bronchodilator FEV1/FVC <0.7. ACO was defined as bronchodilator response (BDR) greater than 15% and 400 mL and/or blood eosinophil count at least 300/μL; these criteria were applied to both cohorts, yielding 111 eligible participants from the ISAR cohort and 1781 from the larger KOCOSS cohort.
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[U]sing simple criteria allows us to screen for ACO patients and enable personalized medicine. Further studies are needed to investigate optimal treatments for those who have high probability of ACO.
A total of 161 patients from the severe asthma cohort and 2181 from the COPD cohort were included in the study. Patients from the 2 cohorts were divided into 4 groups for analysis: pure severe asthma from the ISAR cohort (n=86), ACO from the ISAR cohort (n=25), pure COPD from the KOCOSS cohort (n=1378), and ACO from the KOCOSS cohort (n=403).
Among the 428 patients from both cohorts defined as having ACO, 413 were classified based on eosinophil count criteria and 13 based on the extreme BDR criteria, with 2 patients meeting both criteria. The ACO prevalence was 22.5% (25 of 111) in the severe asthma cohort and 22.6% (403 of 1781) in the COPD cohort.
Patients with ACO from the COPD cohort vs those with ACO from the asthma cohort were more likely to be male (96% vs 48%, P <.01), older (68.4 [7.7] years vs 57.4 [10.9] years, P <.01), and to have allergic rhinitis (68% vs 10%) and atopy (100% vs 3%).
In comparing lung function between patients with ACO from the asthma vs COPD cohorts, the investigators found no significant difference in mean [SD] percent predicted FEV1 (61.1 [16.9] vs 58.4 [18.4], respectively) but that mean percent of predicted FVC was higher in those with ACO from the asthma cohort (90.6 [20.1] vs 80.3 [16.6], respectively).
With respect to the use of inhaled corticosteroid (ICS)-containing inhalers, investigators found that most patients in the severe asthma cohort (94.2% of those with pure asthma and 90% of those with ACO) were prescribed inhalers, compared with about a third of those in the COPD cohort (34.5% of those with pure COPD and 36.7% of those with ACO).
The incidence of moderate-to-severe exacerbation was 22.7% in those with pure severe asthma, 37.5% in those with ACO from the severe asthma cohort, 47.0% in those with ACO from the COPD cohort, and 38.9% in those with pure COPD.
Study limitations include the inclusion of only patients who were Korean; use of data involving patients who were all symptomatic and thus likely not to have mild disease; potential overestimation of ACO due to the definition used; and an unequal number of patients in the asthma and COPD cohorts.
In conclusion, the researchers highlighted the findings that “the risk of exacerbation during a year did not differ between ACO-asthma and ACO-COPD groups,” and that “Treatment options were quite different between the two ACO groups, particularly ICS use.” The investigators also noted that “[U]sing simple criteria allows us to screen for ACO patients and enable personalized medicine. Further studies are needed to investigate optimal treatments for those who have high probability of ACO.”
