Abstract Rationale Lower respiratory tract infections, including community-acquired pneumonia (CAP), are a frequent cause of death worldwide. Predictors of disease severity are needed to identify high-risk patients with CAP who may benefit from early escalation of care and continuous monitoring to detect complications and reduce mortality. Eosinopenia has been reported as a marker of severity in bacterial infections. However, the role of eosinopenia for predicting short-term outcomes in hospitalized patients with CAP is poorly understood. Methods PubMed and Google Scholar were searched from inception to October 2024 for Randomised Controlled Trials (RCTs) and observational studies investigating the role of eosinopenia (50 cells/µL or 2%) in predicting outcomes in patients with CAP. After careful screening, four observational studies involving 13,250 patients were analysed using the random-effects model in RevMan 5.4.1, and Odds Ratios (OR) were calculated. Results Eosinopenia was significantly associated with higher odds of in-hospital mortality (OR 1.74, 95% CI 1.21-2.49, P = 0.003), mechanical ventilation (OR 1.72, 95% CI 1.18-2.51, P = 0.005), and ICU admission (OR 1.90, 95% CI 1.22-2.97, P = 0.004). There was no significant association with requirement for non-invasive ventilation (NIV) (OR 1.16, 95% CI 0.91-1.47, P = 0.23). In the subgroup of patients with COPD and superimposed CAP, eosinopenia was a strong predictor of corticosteroid use (OR 3.14, 95% CI 2.64-3.73, P 0.00001, I²=0%) and mechanical ventilation (OR 3.05, 95% CI 1.97-4.71, P 0.00001, I²=0%), compared with a more modest association in the general CAP population (OR 1.39, 95% CI 1.23-1.57, P 0.00001). Discussion Eosinopenia can serve as a marker of severe disease progression in CAP, particularly in COPD exacerbations and a negative predictor for mortality, ventilation, and ICU admission. The lack of association with NIV may reflect its role in detecting decompensation beyond stages of requirement for NIV. Mechanistically, eosinopenia likely integrates stress response intensity and bacterial burden. Its universal availability supports use in resource-limited settings for risk stratification. Future large scale, controlled studies should standardize eosinophil thresholds, adjust for pre-admission steroids, and test eosinopenia-guided early intervention protocols. This abstract is funded by: None
Asghar et al. (Fri,) studied this question.