Diagnostic Value of Systemic Immune Inflammation Index in Pre-Operative Acute Appendicitis : A Cross Sectional Study at Reference Tertiary Hospital of Hodeidah, Yemen

الملخص

Background: Acute appendicitis is a common surgical emergency with variable clinical severity, ranging from uncomplicated inflammation to complicated forms associated with perforation and increased morbidity. Early identification of complicated cases is essential for optimal management. Recent evidence suggests that inflammatory biomarkers, particularly the Systemic Immune-Inflammation Index (SII), may improve pre-operative risk stratification. Objective: This study aimed to evaluate the diagnostic performance of SII in distinguishing uncomplicated from complicated acute appendicitis. Methodology : A cross-sectional study was conducted on 255 patients with clinically confirmed acute appendicitis. Sociodemographic, clinical, and laboratory data were analyzed. SII was calculated from complete blood count parameters. Patients were classified into uncomplicated and complicated appendicitis groups. Statistical analysis included comparison of means, Mann–Whitney U test, receiver operating characteristic (ROC) curve analysis, and binary logistic regression. Results: The mean age of participants was 14.5 ± 2.9 years, with males forming the majority. Right lower quadrant pain, fever, nausea, vomiting, and anorexia were the most common presenting symptoms. The mean SII was 2011.4 ± 1807.4. Patients with complicated appendicitis (25.1%) demonstrated significantly higher SII levels compared to those with uncomplicated appendicitis (3849.3 vs. 1395.5; p < 0.001). ROC analysis showed excellent diagnostic performance of SII with an AUC of 0.881 (95% CI: 0.812-0.950). With a cut-off value of 2384 (95% CI: 2150 – 2620) used to determine the optimal level, the results showed a sensitivity of 70.3% (95% CI: 57.6% – 81.1%), specificity of 91.6% (95% CI: 86.8% – 95.1%), PPV of 73.8% (95% CI: 60.9% – 84.2%), and NPV of 90.2% (95% CI: 85.1% – 94.0%). This study suggests that the SII clearly beats random guessing and can serve as a reliable clinical marker for identifying complications. Logistic regression revealed that SII was an independent predictor of complicated appendicitis (OR = 2.91 per 1000-unit increase; 95% CI: 2.15–3.94; p < 0.001). Conclusion: SII is an independent and economic biomarker for predicting complicated acute appendicitis with high specificity and good overall diagnostic accuracy. It may serve as a valuable adjunct tool in early pre-operative risk stratification when used alongside clinical and imaging findings.