Blood Eosinophils and Clinical Outcome of Acute Exacerbations of Chronic Obstructive Pulmonary Disease: A Systematic Review and Meta-Analysis

Numerous studies have shown the association between eosinophilia and clinical outcomes of patients with acute exacerbation of chronic obstructive pulmonary disease (AECOPD). But the evidences are lack of consensus.The aim of this meta-analysis was to conduct a pooled analysis of outcome comparing eosinophilic (EOS) AECOPD and non-EOS AECOPD patients.We included PubMed, EMBASE, Web of Science, and Cochrane databases up to 2020 to retrieve articles. Randomized controlled trials and quasi-experimental studies about patients with and without EOS AECOPD in terms of in-hospital mortality, length of hospital stay, comorbidities, forced expiratory volume in 1 s (FEV1), gender, and BMI were included preclinical studies, review articles, editorials, commentaries, conference abstracts, and book chapters were excluded. The methodologic assessment of studies was performed with the Newcastle-Ottawa Scale and Cochran scale. Comprehensive Rev Man 5 was used for the statistical analysis.Twenty-one studies with 18,041 patients fulfilled the inclusion criteria and were used in this meta-analysis. Comparing to the non-EOS group, those with EOS AECOPD patients had a lower risk for in-hospital mortality (odds ratio (OR) = 0.59, 95% confidence interval [CI] 0.36-0.95, p = 0.03), shorter length of hospital stay (OR = -0.72, 95% CI -1.44 to -0.00, p = 0.05), better FEV1 (mean difference = 0.14, 95% CI 0.08-0.20, p < 0.00001), and a lower risk of arrhythmias (OR = 1.50, 95% CI 1.01-2.21, p = 0.04). In addition, the non-EOS group had a higher percentage of male (OR = 1.34, 95% CI 1.15-1.56, p = 0.0002) than EOS group. The rate of steroid use (OR = 0.82, 95% CI 0.47-1.42, p = 0.48) and BMI (mean difference = 0.43, 95% CI -0.18 to 1.05, p = 0.17] had no difference between 2 groups.The results of our meta-analysis suggest that EOS AECOPD patients have a better clinical outcome than non-EOS AECOPD patients in terms of length of hospital stay, in-hospital mortality, FEV1, and risk of arrhythmias. In addition, the non-EOS AECOPD patients have higher percentage of male than EOS AECOPD patients.