Blood Eosinophil Count Stability in Chronic Obstructive Pulmonary Disease and the Eosinophilic Exacerbator Phenotype

This longitudinal study from the EXCEL COPD cohort evaluated blood eosinophil count (BEC) stability and its relationship with exacerbations. Among 100 patients followed across four annual visits, 18% showed persistently high BEC (>300 cells/μl), 29% intermittent, and 53% never eosinophilic. A one-time BEC measurement missed up to 29% of persistently eosinophilic individuals. Patients with eosinophilic exacerbations had higher CAT scores (+2.8 points, P = 0.04) and a 60% increased annual exacerbation risk compared with noneosinophilic exacerbators. Findings highlight substantial intra-individual variability in BEC and identify an eosinophilic exacerbator phenotype potentially responsive to Th2-targeted therapies.