Blood eosinopenia (≤30/µL) as an early predictor of respiratory failure in community-acquired pneumonia: A prospective multicentre study

Introduction and objectives Lower blood eosinophil counts have been associated with increased mechanical ventilation rates in patients with community-acquired pneumonia (CAP). However, the optimal eosinophil count threshold for identifying CAP patients at high risk of respiratory failure remains undefined. This study aimed to establish an optimal admission eosinophil count as a prognostic biomarker for respiratory failure in CAP.Methods This prospective, multicentre cohort study (PROGRESS) enrolled adult patients (≥18 years) hospitalised with community-acquired pneumonia (CAP). A receiver operating characteristic curve analysis with Youden’s index was applied to identify the optimal eosinophil threshold for predicting mechanical ventilation. Associations were adjusted for corticosteroid use using multivariable regression. Additional outcomes – ICU admission and hospital length of stay – were compared between patients above and below the optimal eosinophil count threshold.Results An eosinophil count threshold of ≤30/µL was optimal for predicting mechanical ventilation. Patients with eosinophil counts ≤30/µL experienced significantly higher mechanical ventilation rates (15.5% versus 7.3%; p < 0.0001; RR 2.12, 95% CI 1.61–2.80), regardless of glucocorticoid treatment. They also exhibited higher ICU admission rates (23.1% versus 10.9%; p < 0.0001; RR 2.11, 95% CI 1.70–2.63) and longer hospital stays among survivors (median 8.0 versus 7.0 days; p < 0.0001).Conclusions Admission eosinopenia (≤30 µL) is a robust, easily measured biomarker that predicts respiratory failure in hospitalised CAP. It supports early risk stratification and may guide timely escalation of care.