Abstract:

Purpose: To investigate the relationship between the systemic immune-inflammatory index (SII) and acute appendicitis (AA). Materials and Methods: We retrospectively evaluated patients aged over 18 years who were diagnosed with AA and underwent surgery at our clinic from January 1, 2019, through July 31, 2022. The patients were divided into three groups: complicated acute appendicitis (CAA), uncomplicated acute appendicitis (UAA), and control. The clinical and laboratory characteristics of the patients evaluated at the emergency department were recorded. The neutrophil/lymphocyte ratio (NLR), the platelet/lymphocyte ratio (PLR), and SII (neutrophil count x platelet count/lymphocyte count) were calculated. Results: The study included a total of 1,456 patients, of whom 628 had UAA, 104 had CAA, and 714 were controls. The NLR, PLR, and SII values were statistically significantly higher in the CAA group than in the control group and the UAA group. The multivariate logistic regression analysis revealed that SII was an independent predictor of CAA development (odds ratio [OR]: 4.65; 95% confidence interval [CI]: 2.31–10.17). The predictive power of SII in the prediction of CAA (area under the curve [AUC]: 0.809) was much higher than that of NLR (AUC: 0.729), neutrophil count (AUC: 0.696), and C-reactive protein (AUC: 0.732) alone. It was determined that an SII value greater than 1,989.2 had a sensitivity of 78.4% and a specificity of 88.5% in predicting CAA development. Conclusion: SII is a simple, inexpensive, and promising marker that could predict both the diagnosis and severity of appendicitis.

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