Patients with eosinophilic chronic obstructive pulmonary disease (COPD) have distinct characteristics compared with COPD patients with a history of asthma (AC), as the latter are characterized by the presence of allergies and more exacerbations but less eosinophilic inflammation, researchers reported in Respiratory Research.
Investigators from the Manchester Academic Health Science Centre at the University of Manchester in the UK sought to understand the similarities and differences between patients with eosinophilic COPD and patients with a clinical diagnosis of both asthma and COPD.
Umme Kolsum and colleagues recruited patients from October 2014 to June 2016 from a research database of COPD patients from primary care. Two groups of patients were recruited; 67 COPD patients with no history of asthma were randomly selected from the database, and 14 COPD patients were specifically selected due to a history of childhood asthma. All patients were aged >40 years, with post-bronchodilator forced expiratory volume in 1 second (FEV1)/forced vital capacity (FVC) ratio <0.7 and >10 pack-year smoking history.
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The AC group was significantly younger (mean: 57 vs 69 years) with an earlier age of diagnosis compared with the COPD group, although the duration of COPD after diagnosis was similar between groups. Pack-year history and inhaled corticosteroid use were similar between groups. More COPD with asthma patients reported chronic bronchitis compared to COPD patients (86% vs 55%), while COPD Assessment Test, St Georgessmentpiratory Questionnaire, and Clinical COPD Questionnaire scores were similar between groups.
In the comparison of AC and blood eosinophil COPD patients, the self-reported prevalence of allergies, including hayfever, and the presence of positive skin prick tests were higher in the AC group, although the total IgE count was similar between groups. The post-bronchodilator FEV1 percent predicted was not different between groups, but the FEV1/FVC ratio was higher in the AC group (mean: 0.52 vs 0.42).
Comparison of sputum eosinophil COPD and AC patients showed similar findings to those observed between blood eosinophil COPD and AC patients; there was a higher prevalence of allergy in AC patients. In addition, AC patients had a significantly higher pre- and post-bronchodilator FEV1 L, FEV1 percent predicted and FEV1/FVC ratios compared to sputum eosinophil COPD patients. Sputum eosinophil percent and absolute counts were higher in sputum eosinophil COPD patients compared with AC patients respectively, with 46.2% of AC patients having a sputum eosinophil count greater than 3%.
The most notable clinical difference between AC patients and both the blood and sputum eosinophil COPD patients was the exacerbation rate. The higher exacerbation rate may be linked to allergic mechanisms in AC patients that are not present in eosinophil COPD patients. The degree of eosinophilic airway inflammation was lower in AC patients compared to both the blood and sputum eosinophil COPD patients.
“Our findings demonstrate that eosinophilic COPD patients have distinct characteristics compared to COPD patients with a history of asthma,” said the authors. “AC patients are characterized by the presence of allergies and more exacerbations, but less evidence of eosinophilic inflammation. These data support the concept that different subgroups exist within the asthma COPD overlap, and should be carefully characterized.”
Reference
- Kolsum U, Ravi A, Hitchen P, et al. Clinical characteristics of eosinophilic COPD versus COPD patients with a history of asthma. Respir Res. 26 April 2017. doi: 10.1186/s12931-017-0559-0
