[Blood eosinophil count and clinical characteristics in patients with bronchiectasis]

Objective: To explore the clinical characteristics of bronchiectasis patients with different levels of peripheral blood eosinophils. Methods: This study was a retrospective study. A total of 162 stable non-cystic fibrosis bronchiectasis patients were enrolled from Capital Medical University, Beijing Tongren Hospital from June 2022 to May 2025. Among them, there were 79 males and 83 females, aging 20-85 (60.27±15.83) years. Blood eosinophil(EOS) count (cells/μl, 100 cells/μl=0.1×10⁹/L) was used as the cut-off value to classify patients into high BEC (blood eosinophil count) group, (Blood EOS≥300 cells/μl), medium BEC group (100 cells/μl≤Blood EOS<300 cells/μl) and low BEC group (blood EOS<100 cells/μl). The differences in general information, clinical symptoms, laboratory tests, pulmonary function and imaging characteristics, modified British Medical Research Council dyspnea scale (mMRC) score, bronchiectasis severity index (BSI), FACED scores, bronchiectasis imaging Reiff score and acute exacerbation events in the past year were compared among the three groups. The risk factors for acute exacerbation hospitalization of bronchiectasis in the three groups were analyzed. Data analysis was performed using SPSS 25.0 and R 4.2.2 software. Results: The proportions of patients with high, medium, and low BEC were 22.22%, 48.77% and 29.01%, respectively. Among the three groups, the comorbidity of rhinitis, sinusitis, nasal polyps, atopic dermatitis, respiratory symptoms, mMRC and CAAT scores, BAS%, BAS count, serum IgE, induced sputum EOS%, FeNO, IL-4, IL-5, positive proportion of allergens, positive proportion of Pseudomonas aeruginosa(PA) in sputum culture, positive proportion of fungi, FEV₁ improvement rate, BSI, Reiff score, the proportion of cylindrical bronchiectasis, the occurrence of acute exacerbations[86.11% (31/36) vs. 49.37% (39/79) vs. 72.34% (34/47), χ²=16.44,P<0.001] and hospitalizations[38.89%(14/36) vs. 22.78%(18/79) vs. 48.94%(23/47),χ²=9.49,P=0.009] were statistically significant among the three groups (P<0.05). The high BEC group had more severe clinical symptoms, a higher prevalence of nasal polyps, higher levels of type 2 inflammatory biomarkers, and a higher frequency of acute exacerbation, but lower rates of hospitalization for acute exacerbation hospitalization, lower BSI score, and less pulmonary imaging involvement. IgE(OR=1.002,95%CI:1.000-1.003,P=0.029) was a risk factor for acute exacerbation hospitalization in high BEC group. MMRC(OR=2.879,95%CI:1.345-6.162,P=0.006) and PA infection(OR=4.427,95%CI:1.129-17.358,P=0.033) were independent risk factors for acute exacerbation hospitalization in the medium BEC group. PA infection(OR=8.649,95%CI:1.932-38.724,P=0.005) was an independent risk factor for acute exacerbation hospitalization in the low BEC group(all P<0.05). Conclusions: BEC level can reveal the phenotypic differences of BEC bronchiectasis. High BEC bronchiectasis is associated with airway type 2 inflammation and allergic reaction, with severe clinical symptoms and frequent acute exacerbation, while low BEC bronchiectasis is associated with more PA infection and higher risk of exacerbation-related hospitalization. Identifying the phenotypic differences of BEC bronchiectasis may provide a basis for personalized treatment of bronchiectasis.