Eosinophilic Bronchiectasis: Prevalence, Severity, and Associated Features-A Cohort Study

Abstract

Background: Bronchiectasis (BE) has been traditionally associated with neutrophilic inflammation, but eosinophilic bronchiectasis (EB) has recently emerged. Data about prevalence, clinical features, and disease severity are lacking. This study aimed to assess the EB prevalence, compare EB with non-EB, evaluate the Type-2 (T2) high endotype in BE (T2-high EB) versus non-T2-high EB, and identify EB predictors. Methods: We conducted a prospective study involving 153 BE patients. The data collected included clinical, radiological, and microbiological findings. BE severity was assessed using the bronchiectasis severity index (BSI), FACED and E-FACED scores, and the bronchiectasis etiology and comorbidity index (BACI). EB was defined as a blood eosinophil count (BEC) ≥ 300 cells/μL, and T2-high EB as BEC ≥ 300 cells/μL with fractional exhaled nitric oxide (FeNO) ≥ 25 ppb. Results: Prevalence was 27% for EB and 20% for T2-high EB. EB patients exhibited poorer lung function and more severe radiologic features, with significantly higher severity scores [BSI, FACED, E-FACED, BACI (p < 0.05)], and a higher median exacerbation rate [4 (2-5) in EB vs. 2 (1-4) in non-EB, p = 0.0002], compared with non-EB patients. T2-high EB patients showed higher severity scores [BSI, FACED, E-FACED (p < 0.05)], as well as worse lung function parameters [FEV₁%, FVC%, FEF _25-75% (p < 0.05)] compared with non-T2-high EB patients. In our study, patients with EB exhibited notably worsened lung function and higher BE severity scores compared with their non-EB counterparts, with exacerbations playing a major role in these differences. We found statistically significant positive correlations between BEC and disease severity scores, such as BSI, FACED, and mMRC, as well as an inverse relationship with pulmonary function. The likelihood of EB being present was significantly higher in association with mMRC ≥ 1 (OR = 2.53; 95% CI, 1.26-5.64), exacerbations/year ≥ 1 (OR = 1.27; 95% CI, 1.0-1.63), and chronic PA colonization (OR = 3.9; 95% CI, 1.08-15.8). Conclusions: EB is a distinct endotype. Dyspnea, exacerbations, and PA colonization may be predictive of EB, emphasizing the importance of early detection for improved outcomes. BEC could serve as a useful biomarker of disease severity to consider when diagnosing EB.

Keywords: Type 2 (T2) inflammation; bronchiectasis; eosinophil; exacerbations.

Figure 1

Flow diagram demonstrating patients’ selection. Abbreviations: ABPA, allergic bronchopulmonary aspergillosis; ILD, interstitial lung disease; EGPA, eosinophilic granulomatosis with polyangiitis; FeNO, fractional exhaled nitric oxide; and T2-High, T(2) high eosinophilic inflammation.

Figure 2

Distribution of microbiology in patients with and without EB in relation to blood eosinophilic cell count. (microbiology refers to any isolation of this pathogen in sputum during the registry visit or within the previous year).

Figure 3

Scatter diagrams and regression lines (95% CI) showing the correlations between blood eosinophils count in the whole population with BSI (n) (A); exacerbations (n/year) (B); FEV1 (L) (C); FACED (n) (D); mMRC (E); FEF _25–75% (L) (F); Reiff score (G); Lobes (n) (H). All parameters are expressed as median values (IQR); r: Spearman coefficient. Abbreviations: FEV₁, forced expiratory volume in the 1st second; BSI, bronchiectasis severity index; mMRC, modified Medical Research Council scale; and FEF_25–75 (L), forced expiratory flow between 25% and 75% of FVC.

Figure 4

Receiver operating characteristics (ROC) of the optimal multiple regression model of variables [age, sex (F), BMI (kg/m²), COPD, chronic rhinosinusitis, BACI, mMRC, hemoptysis, BSI, FACED, exacerbations/year, chronic Pseudomonas infection and FEV₁ (%)], strongly associated with comorbid eosinophilic bronchiectasis. The resulting accuracy of this model using the area under the curve (AUC) of the receiver operating characteristics (ROC) was 79% (95% CI: 71–88), with a specificity of 77% and a sensibility of 65%, p < 0.0001.