Clinical Characteristics and Outcomes of Eosinophilic Exacerbations of COPD

Matthew Donnan,1 Tong Lei Liu,1 Matthew Gvalda,1 Xinye Chen,1 Chuan T Foo,1,2 Martin Ian MacDonald,1,2 Francis Thien1,2 1Department of Respiratory Medicine, Eastern Health, Melbourne, Victoria, Australia; 2Faculty of Medicine, Nursing and Health Sciences, Monash University, Melbourne, Victoria, AustraliaCorrespondence: Francis Thien, Department of Respiratory Medicine, Eastern Health, 5 Arnold St, Box Hill, Melbourne, Victoria, 3128, Australia, Email [email protected]: The role of eosinophilic inflammation in exacerbations of chronic obstructive pulmonary disease (COPD) is increasingly recognised. Eosinophilic exacerbations have previously been associated with shorter hospital length of stay and lower inpatient mortality. The objective of this study was to examine clinical characteristics of hospitalised COPD exacerbations stratified by admission eosinophil count.Methods: We performed a retrospective cohort study of exacerbations of COPD at an Australian tertiary health service between 1st October 2019 and 30th September 2020 that were identified using ICD-10 discharge codes. Patients were excluded if they received any systemic corticosteroids prior to hospitalisation. Admissions were stratified according to blood eosinophil count as high eosinophil (HE, ≥ 2% total white blood cell count), or low eosinophil (LE, < 2%).Results: Four hundred and six patients were analysed. HE patients were younger (74.7 vs 77.7 years, p=0.001) and had fewer co-morbidities (1 [1– 2] vs 2 [1– 3], p=0.044). Patients with HE were less likely to be taking inhaled corticosteroids (59% vs 71%, p=0.017). HE exacerbations had a higher blood eosinophil count (0.31 vs 0.06 × 109/L, p< 0.0001), lower total white cell count (8.45 vs 10.6, p< 0.001), lower CRP (10.4 vs 26.7, p< 0.001), fewer infections (29.5% vs 52.1%, p< 0.001) and less oxygen requirement (35.2% vs 46.8%, p=0.036). HE exacerbations had a shorter length of stay (3.56 vs 4.40 days, p=0.047) but similar inpatient mortality.Discussion: Eosinophilic exacerbations of COPD were phenotypically different, affect a younger, less co-morbid population and were associated with shorter length of stay. This may be useful to help prognosticate clinical outcomes and guide clinical management.Plain Language Summary: Exacerbations of COPD are common and carry high morbidity and mortality. Some exacerbations are associated with eosinophilic inflammation, but greater detail surrounding the relationship between eosinophils and exacerbations of COPD is needed. In our study, eosinophilic exacerbations of COPD were found to affect a younger, less co-morbid population, were less likely to be associated with infection, require less oxygen and were associated with shorter length of stay, but had similar rates of inpatient mortality.Keywords: COPD, exacerbation, eosinophils, mortality, length of stay