Analysis of clinical characteristics, prognosis and influencing factors in patients with bronchiectasis-chronic obstructive pulmonary disease overlap syndrome: A prospective study for more than five years.

Background: Considering the large population of bronchiectasis and chronic obstructive pulmonary disease (COPD) patients in China, we aimed to conduct a thorough analysis that investigates the clinical characteristics and prognosis of bronchiectasis-COPD overlap syndrome (BCOS). Further, we aimed to explore factors associated with acute exacerbation and death in BCOS, which may be of value in its early diagnosis and intervention. Methods: We recruited inpatients with COPD from the second Xiangya Hospital of Central South University in China in August 2016, with follow-up until March 2022. Patients in the BCOS group had to meet the criteria for diagnosing bronchiectasis. We used self-completion questionnaires, clinical records, and self-reported data as primary data collection methods. We used Kaplan-Meier survival analyses and Cox proportional hazard models to assess the risk of severe acute exacerbation and death for BCOS during the follow-up period. Results: A total of 875 patients were included and followed up. Patients in the BCOS group had more females, fewer smokers, lower discharge COPD assessment test (CAT) scores, lower forced vital capacity (FVC), a higher likelihood of co-occurring active tuberculosis, higher levels of eosinophils and inflammatory markers, and a higher rate of positive sputum cultures for Pseudomonas aeruginosa than patients in the COPD-only group. Patients in the acute exacerbation group (AE+) were found to have lower body mass index (BMI), more frequent acute exacerbations, higher modified Medical Research Council (mMRC) dyspnoea grade on admission, higher inflammatory markers, lower FVC, higher rates of using inhaled bronchodilators, and higher rates of both positive and Pseudomonas aeruginosa positive sputum cultures. Patients in the 'death' group were older, had a lower BMI, had spent longer time in the hospital, had higher mMRC dyspnoea grade and CAT scores upon admission and discharge, had higher levels of inflammatory markers, lower rates of using inhaled bronchodilators, were more likely to have a combination of pulmonary heart disease and obsolete pulmonary tuberculosis, as well as a higher rate of fungus-positive sputum cultures. Both erythrocyte sedimentation rate at baseline and Pseudomonas aeruginosa culture positivity were confirmed as independent predictors of severe acute exacerbation in multivariate analysis during the years of follow-up. Fungus culture positivity baseline blood urea nitrogen, baseline lymphocyte count, comorbidities with obsolete pulmonary tuberculosis and comorbidities with pulmonary heart disease were verified as independent predictors of death in multivariate analysis during the years of follow-up. Kaplan-Meier curves under survival analysis demonstrated no statistically significant difference in mortality between the COPD and the BCOS groups at the full one, two, and three years of follow-up. Conclusions: Patients with BCOS present with reduced lung function, increased susceptibility to different complications, elevated blood eosinophils and inflammatory markers, and elevated rates of positive Pseudomonas aeruginosa cultures. These distinctive markers are linked to a greater risk of severe acute exacerbations and mortality.