Prognostic role of blood eosinophils in acute exacerbations of chronic obstructive pulmonary disease: systematic review and meta-analysis.

Acute exacerbation of chronic obstructive pulmonary disease (AECOPD) is a major cause of hospitalization and mortality worldwide. While blood eosinophils have been suggested as a prognostic biomarker of COPD, their predictive value in AECOPD remains uncertain. This meta-analysis aims to evaluate the prognostic role of blood eosinophil counts in predicting mortality and hospital readmission in these patients. A systematic review and meta-analysis were conducted according to PRISMA guidelines. We included studies that evaluated the prognostic role of blood eosinophils in AECOPD, with predefined cut-offs. Data on mortality and readmission rates were extracted, and statistical analyses were performed to assess sensitivity, specificity, and likelihood ratios. A total of 14 studies with 23,625 patients were included. High blood eosinophil counts during AECOPD hospitalization had low sensitivity (28.1%) and specificity (66.2%) in predicting 12-month mortality and readmission. Positive and negative likelihood ratios were also suboptimal, with values of 0.8 and 1.1, respectively. Sensitivity analyses, including only high-quality studies, confirmed these findings. The results suggest that blood eosinophil counts have limited prognostic value in predicting mortality and readmission in AECOPD patients. The variability in eosinophil cut-offs and lack of consistent data across studies contribute to this limitation. Further large-scale prospective studies are needed to clarify the role of eosinophils as a prognostic marker in AECOPD. Consequently, routine measurement of blood eosinophils during acute exacerbations may not be warranted for prognostic purposes.