Elevated Eosinophil Counts in Acute Exacerbations of Bronchiectasis: Unveiling a Distinct Clinical Phenotype

Abstract Background Non-cystic fibrosis bronchiectasis is a chronic respiratory disease characterized by bronchial dilation. However, the significance of elevated eosinophil counts in acute exacerbations of bronchiectasis remains unclear. Methods This retrospective case-control study included 169 hospitalized patients with acute exacerbations of non-cystic fibrosis bronchiectasis. Based on blood eosinophil levels, patients were categorized into eosinophilic and non-eosinophilic bronchiectasis groups. Various clinical variables, including lung function, comorbidities and clinical features were collected for analysis. The study aimed to examine the differences between these groups and their clinical phenotypes. Results Eosinophilic bronchiectasis (EB) was present in approximately 22% of all hospitalized patients with bronchiectasis, and it was more prevalent among male smokers (P < 0.01). EB exhibited greater severity of bronchiectasis, including worse airway obstruction, higher scores in the E-FACED (FACED combined with exacerbations) and bronchiectasis severity index (BSI), a high glucocorticoids medication possession ratio, and increased hospitalization cost (P < 0.05 or P < 0.01). Furthermore, we observed a significant positive correlation between blood eosinophil count and both sputum eosinophils (r = 0.49, P < 0.01) and serum total immunoglobulin E levels (r = 0.21, P < 0.05). Additional analysis revealed that patients with EB had a higher frequency of shortness of breath (P < 0.05), were more likely to have comorbid sinusitis (P < 0.01), and exhibited a greater number of lung segments affected by bronchiectasis (P < 0.01). Conclusions These findings suggest that EB presents a distinct pattern of bronchiectasis features, confirming the notion that it is a specific phenotype.