Evaluation of Inflammatory Response in Patients with Bronchiectasis: Eosinophilic and Non-eosinophilic Phenotypes

To examine the distribution of eosinophilic and non-eosinophilic phenotypes, defined by routine complete blood count, in a Turkish bronchiectasis cohort, and to evaluate their associations with demographic and radiological characteristics as geographic validation of European findings.

We retrospectively analyzed 120 patients with bronchiectasis at Yozgat Bozok University Research and Application Hospital. Patients were classified as eosinophilic (≥300 cells/μL) or non-eosinophilic (<300 cells/μL) based on peripheral blood eosinophil count. Demographic, laboratory, and computed tomography radiological extent data (number of lobes involved) were compared between groups. Correlation analyses, exploratory logistic regression, and receiver operating characteristic analyses were performed, with multiple-comparison correction and sensitivity analyses (alternative cutoffs, exclusion of inhaled corticosteroid users).

Twenty-five patients (20.8%) were eosinophilic and 95 (79.2%) were non-eosinophilic. The eosinophilic group was younger (52.1±12.0 vs. 60.3±13.5 years; P = 0.005; Cohen's d = -0.62), but this lost significance after multiple-comparison correction; other demographic and laboratory variables did not differ. Radiological extent was similar between groups (P = 0.606) and did not correlate with eosinophil count (rho = 0.11, P = 0.227). In an exploratory multivariate model, only age was independently associated with the eosinophilic phenotype (adjusted odds ratio = 0.95, 95% confidence interval 0.92-0.99; P = 0.009). Eosinophil count, neutrophil count, and C-reactive protein showed limited discrimination for extensive radiological involvement, with area under the curves of 0.52, 0.50, and 0.58, respectively; lobar distribution did not differ (P = 0.655 and 1.000). Radiological findings were similar after excluding inhaled corticosteroid users (n = 23).

Hemogram-based phenotyping was feasible, but eosinophil count alone had limited value in predicting radiological extent or distribution. These preliminary single-center, retrospective data will be included in a planned multicenter study pending ethical approval.