Patients with asthma–chronic obstructive pulmonary disease overlap (ACO) experienced a higher burden of disease than patients with either asthma or COPD alone, a recent study has found.
Approximately 20% of chronic obstructive airway disease cases are ACO, but data on these patients are limited, as they are often excluded from clinical trials, wrote Sarah A. Hiles, MD, of the University of Newcastle (Australia) and colleagues.
“Comparing the burden of eosinophilic ACO, eosinophilic severe asthma, and eosinophilic COPD may also help contextualize findings from phenotype-targeted treatments in different diagnostic groups, such as the limited success of anti-IL [interleukin]–5 monoclonal antibodies as therapy in eosinophilic COPD,” they said.
In a cross-sectional, observational study published in Respirology the researchers recruited patients aged 18 years and older with a confirmed diagnosis of COPD only (153) severe asthma only (64), or ACO (106). Patients were assessed for demographic and clinical factors including health-related quality of life, past-year exacerbation, and other indicators of disease burden. In addition, patients were identified as having eosinophilic airway disease based on a blood eosinophil count of at least 0.3x109/L.
Overall, eosinophilic airway disease was present in 41% of the patients; 55%, 44%, and 29% for those with ACO, severe asthma, and COPD, respectively. Reports of poor health-related quality of life and past-year exacerbations were similar for eosinophilic patients across all three conditions.
However, patients with eosinophilic ACO experienced significantly more past-year exacerbations, notably those requiring oral corticosteroids, compared with patients with asthma alone. In addition, the cumulative number of past-year exacerbations in patient with eosinophilic disease was 164 in those with ACO, compared with severe asthma alone (44) and COPD alone (59).
Patients with ACO also had significantly higher disease burden based on the St. George’s Respiratory Questionnaire (SGRQ), which assessed functional limitation. “For 100 patients, the cumulative SGRQ score attributable to eosinophilic airways disease in ACO was 2,872.8, which was higher than in severe asthma (1,942.5) or COPD (1,638.1),” the researchers said.
The study was limited by several factors including the cross-sectional design and use of a single measurement to classify eosinophilia, the researchers noted. “The non-eosinophilic group likely included a mix of patients with treated eosinophilia and patients without eosinophilia, regardless of treatment, which is a limitation to consider when interpreting the disease burden estimates in this group,” they added.
However, the results add to the understanding of blood eosinophils in airway disease and the study “supports eosinophilia as a phenotype that spans across disease labels of severe asthma and COPD, and their overlap,” they concluded.
The study was supported by AstraZeneca; lead author Dr. Hiles received a salary through a grant from AstraZeneca to the University of Newcastle while conducting the study. Other coauthors disclosed relationships with companies including AstraZeneca, GlaxoSmithKline, Menarini, and Novartis.