Study Defines Subgroups Within Asthma/COPD Overlap
Patients with eosinophilic COPD are a distinct subgroup and should not be categorized with COPD patients with asthma, researchers reported. COPD patients with asthma tend to have more allergies and more exacerbations than patients with eosinophilic COPD, who have more eosinophilic inflammation.
“The asthma-COPD overlap consists of multiple subgroups of patients with distinct clinical and pathophysiological features, and there is a need to further define the characteristics of these subgroups,” wrote Umme Kolsum and colleagues from Manchester Academic Health Science Centre at the University of Manchester in the United Kingdom.
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Using a research database of COPD patients from primary care, Kolsum and colleagues compared clinical characteristics of 2 groups of patients—those with eosinophilic COPD who did not have childhood asthma, and COPD patients who did have childhood asthma (AC). The researchers randomly selected 67 patients with COPD and no asthma history, while 14 patients with COPD were purposely selected because they had a history of childhood asthma. In addition, 14 of the 67 COPD patients without asthma had a blood eosinophil count ≥300 cells/μl and were termed COPD blood eosinophilhigh, whereas 24 patients had a sputum eosinophil count ≥3% and were termed COPD sputum eosinophilhigh.
Patients in all groups were aged 40 years or more, had smoked for more than 10 pack years, and had post-bronchodilator forced expiratory volume in 1 second (FEV1)/forced vital capacity (FVC) ratio <0.7.
Analysis of clinical characteristics indicated that the exacerbation rate was the most significant difference between AC patients and blood and sputum eosinophilhigh COPD patients. This difference in exacerbation rate may result from allergic mechanisms that are found in AC patients but not in eosinophilhigh patients. AC patients also had less eosinophilic airway inflammation than the blood and sputum eosinophilhigh COPD patients. According to the researchers, these distinct airway inflammation characteristics offer additional evidence that AC patients and eosinophilic COPD should not be categorized in the same subgroup.
The researchers concluded that “eosinophilic COPD patients have distinct characteristics compared to COPD patients with a history of asthma. 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.”
—Lauren LeBano
Reference
1. Kolsum U, Ravi A, Hitchen P, Maddi S, Southworth T, Singh D. 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.