Clinical Characteristics and Outcomes of Eosinophilic Exacerbations of COPD

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.

We performed a retrospective cohort study of exacerbations of COPD at an Australian tertiary health service between 1^st October 2019 and 30^th 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%).

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.

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.