Association Between Eosinophils and Readmission in Patients with Eosinophil-Fluctuating AECOPD: A Multi-Threshold PWP-GT Analysis

Purpose: Although peripheral blood eosinophils (EOS) have been extensively studied as a biomarker for chronic obstructive pulmonary disease (COPD), the association between EOS and COPD prognosis remains controversial. Our objective was to analyze the relationship between EOS and readmission in patients with EOS-fluctuating COPD. Patients and Methods: This is a retrospective, single-center study of inpatients admitted to the Department of Respiratory and Critical Care Medicine at Anhui Second People’s Hospital between January 2021 and June 2026 due to at least two acute exacerbations of COPD (AECOPD). Prentice–Williams–Peterson Gap Time (PWP-GT) models were established using EOS thresholds of 100cells/ μL, 200cells/ μL, 30cells/ μL, 1%, 2%, and 3%. The relationship between EOS levels at the time of the previous hospitalization and the time interval until the next hospitalization was analyzed. Results: The study included 224 patients and 1095 hospitalizations. EOS ≥ 300 cells/ μL (HR = 0.767, 95% CI: 0.602– 0.977, P = 0.032) and EOS% ≥ 3% (HR = 0.804, 95% CI: 0.671– 0.965, P = 0.019) were independent protective factors against readmission. EOS ≥ 100 cells/μL (P = 0.070), EOS ≥ 1% (P = 0.100), EOS ≥ 2% (P = 0.094), and EOS ≥ 200 cells/μL (P = 0.189) were not significantly associated with readmission. The protective effects of EOS ≥ 300 cells/μL and EOS% ≥ 3% were consistent across subgroup analyses stratified by sex, history of acute exacerbations, mechanical ventilation, and comorbidities. The protective effect of EOS was more pronounced in patients aged < 65 years and in those using inhaled pharmacotherapy. Conclusion: Patients with EOS-fluctuating AECOPD have a unique prognostic profile. Higher eosinophil levels were associated with a lower risk of rehospitalization. Keywords: chronic obstructive pulmonary disease, acute exacerbation, eosinophils, prognosis