Composite Biomarkers in Neonatal Sepsis Assessing SII and SIII

Abstract

Early risk stratification in neonatal sepsis is essential for timely intervention. Single biomarkers like CRP, NLR, and PLR provide limited insight. Composite inflammatory indices may offer better diagnostic and prognostic value. The aim of the study was to compare and contrast the ability of the Sepsis Inflammatory Index SII and the Systemic Immune-Inflammation Index SIII to predict outcomes in neonatal sepsis. In this prospective observational study of 147 neonates, SII was calculated as (NLR × CRP) + (PLR ÷ 10), and SIII as (Neutrophil count × Platelet count) ÷ Lymphocyte count. Logistic regression and Receiver Operating Characteristic (ROC) analysis were performed to estimate diagnostic accuracy to predict mortality, ventilation need, and stay in NICU. SII had the highest area under the curve (AUC = 0.81), followed by SIII (AUC = 0.71), CRP (AUC = 0.69), and NLR (AUC = 0.68). SII ≥ 15 predicted mortality with 84.6% sensitivity and 75.5% specificity. SIII > 450 was significantly associated with need for mechanical ventilation (aOR 3.61). SII and SIII are robust, easily derived indices that outperform traditional single biomarkers in neonatal sepsis risk stratification. They are highly applicable in NICU settings, especially in low-resource contexts.