Eosinopenia as a marker of diagnosis and prognostic to distinguish bacterial from aseptic meningitis in pediatrics

Procalcitonin (PCT) has proven its efficacy to distinguish bacterial from aseptic meningitis in children. Nevertheless, its use in routine is limited by its cost and availability, especially in low- and middle-income countries. It is now acknowledged that eosinopenia is a marker of infection and/or severity of the systemic inflammatory response. Although no study ever demonstrated that eosinopenia could differentiate bacterial from viral infection, we decided to conduct a study concerning meningitis in children. This bicentric and retrospective study was conducted between January 2012 and October 2018, in children hospitalized for meningitis. The white blood cell was systematically gathered at the admission to evaluate the eosinophil count. Characteristic data were compared between 2 groups: documented bacterial meningitis (DBP) and aseptic meningitis which includes documented viral meningitis (DVM) and non-documented meningitis (ND). Among 190 patients admitted for meningitis, 151 were analyzed, including DBM (n = 45), DVM (n = 73), and ND (n = 33) meningitis. Groups were comparable. Mean age was 33 ± 48 months with a sex ratio of 1.6. Mean of eosinophil count was 15 ± 34/mm³ in the DBM group versus 132 ± 167/mm³ for the aseptic meningitis group (p < 0.0001). Best threshold for the diagnosis of bacterial meningitis was an eosinophil count < 5/mm³ with a sensitivity of 80% and specificity of 73% and a likelihood ratio of 2.9. Eosinopenia seems to be a reliable and non-invasive marker of bacterial meningitis in pediatrics. The absence of extra cost makes it very interesting in low- and middle-income countries or when usual biomarkers such as PCT are unavailable.