Blood eosinophil count and exacerbation risk in patients with COPD

Exacerbations in chronic obstructive pulmonary disease (COPD) are major contributors to worsening lung function, impaired quality of life, emergency healthcare use and COPD-related mortality. COPD exacerbations are heterogeneous in terms of airway inflammation and aetiology. About 60% of COPD patients have blood eosinophil counts of ≥2%, which appears to be associated with an increased risk of exacerbations [1–3]. However, the association between blood eosinophil counts at stable disease and COPD exacerbations in the subsequent year is incompletely understood.