Eonisophil-to-lymphocyte ratio and early variation as predictors of severity and in-hospital mortality in patients admitted to the emergency department for SARS-CoV-2 infection.

Since its emergence in 2019, the study of biomarkers in COVID-19 has focused on predicting the course of this potentially fatal disease. The eosinophil-to-lymphocyte ratio (ELR) appears to be a new indicator of systemic inflammation, morbidity, and mortality in inflammatory, allergic, and cancer. The aim of our study was to determine the prognostic value of ELR and its early variation in predicting in-hospital mortality and severity in emergency department (ED) patients with SARS-CoV-2 infection. Between March 1 and April 30, 2020, we conducted a multicenter, retrospective study in 6 major hospitals in northeastern France. The cohort included patients with a confirmed diagnosis of SARS-CoV-2 infection (moderate-to-severe disease) hospitalized after admission to the ED. A total of 1,035 patients were included in this study. The ELR at 24 h (odds ratio: 0.0054; 95% confidence interval: 0.0001 to 0.2523; P = 0.008) was associated with severity of infection. The only biochemical factor significantly associated with mortality was ΔELR at 24 h (i.e. the difference between ELR values at 24 h and at admission) (odds ratio: 0.0305; 95% confidence interval: 0.0026 to 0.3626; P = 0.006) in univariate analysis. The best ELR threshold for predicting severity of infection was found with the ELR at 24 h with a result of 0.0007 (sensitivity 63.8%, specificity 61%), and for predicting mortality, ΔELR at 24 h found significant values with a threshold of -0.013 (sensitivity 77.4%, specificity 8.48%). In conclusion, ELR at 24 h after ED admission may be a potentially useful biomarker for early prediction of severity of SARS-CoV-2 infection, but its isolated use remains limited for mortality prediction.