The Clinical Utility of Serum Biomarkers in the Differentiation and Prognostic Assessment of Viral Meningitis

Background and Objectives: Viral meningitis presents significant diagnostic challenges. The aim of this study was to identify predictive factors for meningitis etiology and clinical outcomes. Methods: This prospective, single center, comparative study enrolled patients meeting clinical, biological, and microbiological criteria for bacterial (BM) or viral (VM) meningitis. Serum inflammatory markers, namely the neutrophil-to-lymphocyte ratio (NLR), platelet-to-lymphocyte ratio (PLR), and systemic immune-inflammation index (SII), were quantified. In addition, the concentrations of oxidative stress biomarkers, glutathione peroxidase 3 (GPx3) and copper/zinc superoxide dismutase (Cu/Zn SOD), were also determined. Spearman correlation and logistic regression were used to evaluate associations between biomarkers and etiology, while receiver operating characteristic (ROC) curves assessed outcome correlations. Results: VM patients showed a significantly lower NLR (p = 0.007), PLR (p = 0.010), and SII (p = 0.016), with higher GPx3 (p < 0.0001) levels compared with BM patients. Cu/Zn SOD showed no significant difference (p = 0.442) between groups. Multivariate logistic regression identified the SII (OR = 1.015; 95% CI = 1.004–1.026) and GPx3 (OR = 0.847; 95% CI = 0.740–0.970) as etiology predictors. The SII was the strongest predictor of mortality in VM (AUC = 0.833). Conclusions: Serum markers of inflammation, including the systemic immune–inflammation index, along with antioxidant indicators such as GPx3, may serve as valuable additional tools for predicting meningitis etiology and forecasting patient outcomes.