The role of non-invasive modalities for assessing inflammation in patients with non-cystic fibrosis bronchiectasis

Abstract

Introduction: Bronchiectasis is a heterogeneous entity, taking into account clinical characteristics, inflammatory response, effectiveness of treatment and frequency of exacerbations. In stable state non-cystic fibrosis (non-CF) bronchiectasis, little is known about non-invasive techniques used for evaluating airway inflammation in obstructive airway diseases.

Objectives: We sought to evaluate the associations between induced sputum and clinical/radiologic characteristics, and the differences between biomarkers expressing Th1 and Th2 response in patients with non-CF bronchiectasis and to compare our findings with a previously studied population of patients with asthma and COPD.

Methods: We evaluated prospectively collected data from subjects with bronchiectasis. Comparisons were made between clinical, radiographic and physiologic characteristics, as well as induced sputum markers using appropriate statistical tools. We compared the levels of sputum markers with those of a previously studied cohort of asthma and COPD patients.

Results: We enrolled 40 subjects (21men, mean age 63.5yrs) with bronchiectasis. Fifteen subjects (37.5%) had a neutrophilic phenotype, 7 (17.5%) had an eosinophilic phenotype, 3 (12.5%) had a mixed neutrophilic-eosinophilic phenotype and 15 (37.5%) had a paucigranulocytic phenotype. Subjects with sputum neutrophilia had more severe bronchiectasis in HRCT and higher levels of IL-8 in sputum, whereas subjects with eosinophilia had higher levels of FeNO, greater bronchodilator reversibility and higher sputum IL-13. Sputum IL-8 levels were higher in subjects exhibiting frequent exacerbations and correlated with neutrophils in sputum (r=0.799), the extent of bronchiectasis in HRCT (r=0.765) and post-bronchodilator FEV₁ (r=-0.416). Sputum IL-13 levels correlated with sputum eosinophils (r=0.656) and bronchodilator reversibility (r=0.441). Neutrophilic bronchiectasis exhibited comparable IL-8 levels to COPD, whereas eosinophilic bronchiectasis showed significantly lower IL-13 levels compared to asthma.

Conclusions: Sputum cell counts and IL-8 and IL-13 correlate with distinct clinical and functional measurements of disease severity and therefore may have a role for non-invasively assessing inflammation in non-cystic fibrosis bronchiectasis.

Keywords: Airway inflammation; Biomarkers; Lung function; Non-cf bronchiectasis; Sputum induction.