Bronchiectasis with Chronic Rhinosinusitis Is Associated with Eosinophilic Airway Inflammation and Is Distinct from Asthma.

RATIONALE:Bronchiectasis is an airway inflammatory disease frequently associated with chronic rhinosinusitis (CRS). An eosinophilic endotype of bronchiectasis has recently been described, but detailed testing to differentiate eosinophilic bronchiectasis from asthma has not been performed. OBJECTIVE:This prospective observational study aimed to test the hypotheses that bronchiectasis with CRS is enriched for the eosinophilic phenotype in comparison with bronchiectasis alone and that the eosinophilic bronchiectasis phenotype exists as a separate entity from bronchiectasis associated with asthma. METHODS:People with idiopathic or post-infectious bronchiectasis were assessed for concomitant CRS. We excluded people with asthma, PCD, and smokers. We assessed sputum and blood cell counts, nasal NO and fractional excreted NO, methacholine reactivity, skin allergy testing and total and specific IgE, cytokines in sputum and serum, and microbiome in sputum and nasopharynx. RESULTS:22 people with CRS (BE+CRS) and 17 without CRS (BE-CRS) were included. Sex, age, Reiff score, and bronchiectasis severity were similar. Median (IQR) sputum eosinophil percentages were 0 (0-1.5)% in BE-CRS, and 3(1-12)% in BE+CRS (p=0.012). Blood eosinophil counts were predictive of sputum eosinophilia (counts ≥3%; AUC 0.68, 95% CI 0.50-0.85) inclusion of CRS improved the prediction of sputum eosinophilia by blood eosinophils (AUC 0.79 (95%CI 0.65-0.94). Methacholine tests were negative in 85.7% BE-CRS and 85.2% BE+CRS (p>0.99). Specific IgE and skin testing were similar between the groups, but total IgE levels were elevated in people with elevated sputum eosinophils. Microbiome analysis demonstrated distinct microbiota in nasopharyngeal and airway samples in both BE+CRS and BE-CRS without significant differences between groups, however, interactome analysis revealed altered interactomes in individuals with high sputum eosinophils and CRS. CONCLUSION:Bronchiectasis with CRS is associated with an eosinophilic airway inflammation that is distinct from asthma.