Peripheral blood eosinophilia and clinical phenotype in Bronchiectasis

Introduction: Eosinophilic phenotypes have been identified in asthma and COPD which can be identified by elevated peripheral blood eosinophil counts. Bronchiectasis is traditionally regarded as a purely neutrophilic disease. But peripheral blood eosinophilia can be observed. We determined the clinical significance of eosinophilia in bronchiectasis. Methods: Single centre observational cohort of patients with HRCT confirmed bronchiectasis. Peripheral blood eosinophil count was measured when clinically stable. Quality of life was measured by the QOL-B respiratory symptom score (RSS). Results: 183 patients were enrolled. Mean age 69.6 years (SD 12.3), 54.1% female. Mean FEV1 77.95 and 2.6 exacerbations per year. Eosiniphil counts were <150cells/ul in 27.3%, 150-299 in 27.3%, 300-400 cells in 18.0% and >400 in 13.1%. No association was observed between eosinophil counts and the frequency of overall exacerbations, but patients with an eosinophil count greater than 300 cells/ul were more likely to have severe exacerbations in multiple logistic regression (OR 2.61 95% CI 1.12-6.12, p=0.02) independent of co-exsting asthma. There was no association between eosinophil count and lung function but eosinophil counts were significantly higher in patients with self-reported asthma (p=0.03), and patients with higher eosinophil counts had worse quality of life using the QOL-B RSS (r=-0.37, p=0.01). Conclusions: this pilot study suggests some association between higher peripheral blood eosinophils counts and more severe disease in bronchiectasis.