Stability of eosinophilic inflammation in COPD bronchial biopsies

Blood eosinophil counts (BEC) predict the response to inhaled corticosteroids (ICS) in COPD patients with increased exacerbation risk [1, 2]. Studies have shown an association between BEC and both sputum and lung tissue eosinophil counts in COPD patients [3, 4], supporting BEC as a biomarker that reflects the degree of eosinophilic lung inflammation. While the long-term stability of BEC in COPD patients has been studied [5–7], the stability of eosinophilic airway inflammation in COPD patients is less clear. Good stability of COPD sputum eosinophil counts up to 3 months has been reported [8, 9], but similar analysis using submucosal eosinophil counts (SMEC) are lacking. Eosinophilic airway inflammation shows greater regional and temporal variability in COPD patients with higher numbers of submucosal eosinophils