Eosinophilic exacerbations of chronic obstructive pulmonary disease (COPD), characterized by high blood eosinophil counts are a distinct COPD phenotype with typical clinical features and outcomes, according to a study published in The International Journal of Chronic Obstructive Pulmonary Disease.¹ They are less often infection-related, require less supplemental oxygen, and are associated with fewer comorbidities and shorter hospital stays.

This retrospective study enrolled 406 COPD patients attending a tertiary health service in Australia from October 2019 to September 2020 with the aim to investigate the clinical characteristics of COPD exacerbations requiring hospitalization, based on eosinophil count at the time of admission. Blood eosinophil counts were categorized as high (≥2% total white blood cell count), or low (<2%). Those who had received systemic corticosteroids prior to hospital admission were excluded.

Compared to the low eosinophil group, patients in the high eosinophil group were younger (74.7 vs 77.7 years) and had fewer comorbidities (median 1 vs 2). Participants with high eosinophil count were also less likely to be receiving inhaled corticosteroids prior to admission (59% vs 71%).

During exacerbations, patients with high eosinophil count showed a significantly higher blood eosinophil count (0.31 vs 0.06 × 10⁹/L), lower total white cell count (8.45 vs 10.6 × 10⁹/L), and lower C-reactive protein levels (10.4 vs 26.7 mg/L). They also had fewer infections (29.5% vs 52.1%) and needed less supplemental oxygen (35.2% vs 46.8%) compared to those with lower eosinophil counts. High eosinophil exacerbations were associated with a shorter hospital stay (3.56 vs 4.40 days), though inpatient mortality was similar between groups.

Findings of this study support the association between exacerbations and eosinophilic inflammation, demonstrating that eosinophilic exacerbations of COPD are common and eosinophilic COPD exacerbations represent a distinct clinical phenotype. Measuring eosinophil count at presentation, as a routine, helps stratify the risk of clinical outcomes, such as duration of hospitalization, and may play a role in guiding individualized treatment decisions. COPD patients with elevated blood eosinophil counts, therefore, should be closely monitored.

Reference

1.   Donnan M, et al. Clinical characteristics and outcomes of eosinophilic exacerbations of COPD. Int J Chron Obstruct Pulmon Dis. 2025 Apr 13:20:1061-1070. doi: 10.2147/COPD.S485246.