Objective To evaluate the correlation between blood eosinophilia and clinical characteristics, readmission rate and mortality in patients with acute exacerbation of chronic obstructive pulmonary disease (AECOPD). Methods PubMed, Embase, Web of Science, Cochrane Library, China National Knowledge Infrastructure, Wanfang Data, VIP, and CBM databases were searched until October 31, 2021. Two researchers independently screened the literature, extracted the data, and evaluated the bias risk of the included studies. Meta-analysis was conducted by Rev Man v.5.4. Results Finally, 76 observational studies met the inclusion criteria, including 15 English literatures and 61 Chinese literatures. There were 8240 patients (34.20%) in the eosinophilia group (EOS≥2%) and 15854 cases (65.8%) in the eosinophil normal group (EOS<2%). Results of meta-analysis: (1) Inflammatory Index: eosinophilia group had lower C-reactive protein [MD=–8.44, 95%CI (–10.59, –6.29), P<0.05], and lower neutrophil to lymphocyte ratio [MD=–2.47, 95%CI (–3.13, –1.81), P<0.05]. (2) Hospitalization: eosinophilia group had shorter hospital stay [MD=–2.23, 95%CI (–2.64, –1.81), P<0.05] and lower in-hospital mortality [OR=0.41, 95%CI (0.31, 0.53), P<0.05], lower mechanical ventilation rate [OR=0.59, 95%CI (0.47, 0.75), P<0.05], lower hormone use rate [OR=0.91, 95%CI (0.85, 0.96), P<0.05]. (3) Follow-up results: eosinophilia group had a lower rate of readmission at 1 year [OR=0.78, 95%CI (0.66, 0.92), P<0.05] and a lower rate of death at 1 year [OR=0.78, 95%CI (0.62, 0.97), P<0.05]. Conclusions AECOPD patients with eosinophilia group were characterized by lower inflammatory indicators, shorter hospital stay, shorter in-hospital mortality, lower mechanical ventilation rate, lower hormone use rate, lower rate of acute exacerbation readmission, lower mortality rate and lower rate of follow-up after 1 year. This kind of patients with mild disease, good treatment effect, low risk of acute exacerbation.
