The Utility of systemic immune-inflammation index and Systemic inflammation response index in differentiating acute appendicitis from other causes of pediatric abdominal pain

The aim of our study is to evaluate the diagnostic value of newly identified inflammatory markers in differentiating acute appendicitis from other abdominal pain causes in pediatric patients. This retrospective study included pediatric patients under 18 presenting to the emergency department with abdominal pain between January 2020 and August 2024. Patients were categorized into two groups: acute appendicitis (Group 2) and non-appendicitis-related abdominal pain (Group 1). Demographic data, clinical presentation, and inflammatory markers such as neutrophil-to-lymphocyte ratio (NLR), platelet-to-lymphocyte ratio (PLR), lymphocyte-to-monocyte ratio (LMR), pan-immune inflammation value (PIV), systemic immune-inflammation index (SII), and systemic inflammation response index (SIRI), were recorded for analysis. A total of 135 patients were included in this study (group 1: 100, group 2: 35). Group 2 had a significantly higher mean age (10.5 ± 4.5 vs. 7.6 ± 3.6 years, p < 0.001). Inflammatory indices were significantly elevated in Group 2 compared to Group 1, including median NLR (5.18 vs. 1.78, p < 0.001), PIV (1232 vs. 353, p = 0.001), SII (1743 vs. 528, p < 0.001), and SIRI (4.41 vs. 1.09, p < 0.001). For diagnosis, SIRI (cut-off > 2.56) demonstrated 80% sensitivity, 71% specificity, and an AUC of 0.772, while NLR (> 4) showed 69% sensitivity and 79% specificity. In multivariate logistic regression analysis, only Age > 11 years (OR = 5.45, 95% CI: 1.9–15.5, p = 0.001) and SIRI > 2.56 (OR = 10.8, 95% CI: 1.5–76.5, p = 0.017) remained as significant independent predictors for acute appendicitis. These markers, combined with clinical findings, can significantly enhance early diagnostic triage in the emergency department. Specifically, the high negative predictive value of SIRI suggests a strong rule-out utility, supporting safe and effective clinical decision-making regardless of whether the subsequent treatment pathway is operative or non-operative.