Aims: Bronchiectasis and asthma often coexist, both marked by chronic inflammation and structural airway changes. The BASIIS study aimed to investigate the link between serum eosinophils, clinical characteristics and airway changes in bronchiectasis patients with an asthma co-diagnosis.

Methods: Retrospective cross-sectional analysis of bronchiectasis disease patients with asthma co-diagnosis. Automatic analysis (LungQ, Thirona, Nijmegen, NL) of bronchus/artery (BA) dimensions and ratios on chest CT. Assessment of correlations between serum eosinophils, clinical characteristics and bronchial wall thickness/artery (Bwt/A), bronchial wall area/outer area (Bwa/Boa), mean airway wall area standardized for 10-mm inner perimeter (Pi10) and number and volume of mucus plugs (MPs).

Results (see table): In 63 participants, eosinophil tertile categories showed no significant differences in Bwt/A,  Bwa/Boa, Pi10, MPs, or other clinical characteristics. By multiple regression, FEV1 correlated inversely with Bwt/A, Bwa/Boa, Pi10 and MPs. Pseudomonas aeruginosa colonization correlated positively with Bwt/A, Bwa/Boa, Pi10, and MPs.

Conclusions: Serum eosinophils did not show an association with clinical or radiological characteristics in bronchiectasis patients with asthma. Yet, we did find associations between airway wall thickness, MPs and FEV1. Pseudomonas colonization was also associated with airway wall thickening and MPs numbers and volume.