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

<b><i>Background:</i></b> 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. <b><i>Objective:</i></b> The aim of this meta-analysis was to conduct a pooled analysis of outcome comparing eosinophilic (EOS) AECOPD and non-EOS AECOPD patients. <b><i>Methods:</i></b> 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. <b><i>Results:</i></b> 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, <i>p</i> = 0.03), shorter length of hospital stay (OR = −0.72, 95% CI −1.44 to −0.00, <i>p</i> = 0.05), better FEV1 (mean difference = 0.14, 95% CI 0.08–0.20, <i>p</i> &#x3c; 0.00001), and a lower risk of arrhythmias (OR = 1.50, 95% CI 1.01–2.21, <i>p</i> = 0.04). In addition, the non-EOS group had a higher percentage of male (OR = 1.34, 95% CI 1.15–1.56, <i>p</i> = 0.0002) than EOS group. The rate of steroid use (OR = 0.82, 95% CI 0.47–1.42, <i>p</i> = 0.48) and BMI (mean difference = 0.43, 95% CI −0.18 to 1.05, <i>p</i> = 0.17] had no difference between 2 groups. <b><i>Conclusion:</i></b> 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.