Predictive Value of the Systemic Immune-Inflammation Index in Pediatric Sepsis: A Prospective Observational Study

Abstract

Background: Pediatric sepsis is a time-critical condition associated with substantial morbidity and mortality. Early identification of children at increased risk remains challenging because the initial clinical presentation may be nonspecific and routinely available inflammatory markers may have limited discriminatory ability. The systemic immune-inflammation index (SII), derived from platelet, neutrophil, and lymphocyte counts, integrates multiple components of the host inflammatory and immune response and may provide a readily accessible marker for risk stratification. Objective: To evaluate the predictive value of SII in children with sepsis and determine its diagnostic performance for identifying pediatric patients with sepsis. Methods: A prospective observational study was conducted in the Department of Pediatrics, Ankur Super-Specialty Children Hospital, Ranchi, over a period of 12 months. Fifty pediatric patients were included. Clinical assessment and routine hematological investigations were performed at enrollment. SII was calculated using the formula: platelet count × neutrophil count / lymphocyte count. Patients were categorized according to the presence or absence of sepsis. SII values were compared between groups, and receiver operating characteristic (ROC) analysis was performed to assess its discriminatory performance. Results: Among the 50 children included, 30 (60.0%) had sepsis and 20 (40.0%) did not have sepsis. The mean SII was substantially higher among children with sepsis than among those without sepsis (980 ± 520 vs 480 ± 250, respectively). ROC analysis demonstrated an area under the curve of 0.80 (95% CI: 0.68–0.92). An SII cut-off value of 650 provided a sensitivity of 76.7% and specificity of 75.0%, with a positive predictive value of 82.1% and negative predictive value of 68.2%. Conclusion: SII demonstrated moderate discriminatory ability for pediatric sepsis in this prospective cohort. The higher SII observed among children with sepsis and the ROC performance at a cut-off of 650 suggest that SII may serve as a useful adjunctive marker for early risk assessment. However, SII should be interpreted together with clinical findings and established investigations rather than used as a standalone diagnostic test. Keywords: pediatric sepsis; systemic immune-inflammation index; SII; neutrophils; lymphocytes; platelets; biomarker; ROC curve; diagnostic accuracy.