Door-to-surgery time and systemic immune-inflammatory indices in acute appendicitis: diagnostic performance and clinical associations

Aim: In acute appendicitis (AA), early differentiation between complicated AA (CA) and uncomplicated AA (UCA) directly affects the treatment process. This study investigated the diagnostic performance of the Systemic Immune-Inflammation Index (SII) and the Systemic Inflammatory Response Index (SIRI) in distinguishing CA from UCA, as well as the association between door-to-surgery time (DST) and clinical outcomes.Materials and Methods: Patients who presented to the emergency department and underwent surgery with a diagnosis of AA between January 1, 2020, and December 31, 2024, were retrospectively evaluated. According to the pathology reports, cases of perforated or gangrenous appendicitis were classified as CA, whereas cases of simple or suppurative/phlegmonous AA were classified as UCA. DST, defined as the time (minutes) from the patient’s admission to the emergency department until the start of surgery, was calculated for each patient.Results: After applying exclusion criteria, 556 patients were included in the analysis. Of the patients, 16.9% (n=94) were classified as CA, and 83.1% (n=462) as UCA. In the CA group, median age, monocyte count, C-reactive protein (CRP), SII, and SIRI were significantly higher, whereas lymphocyte count was significantly lower. In ROC analysis, CRP showed the highest diagnostic performance (AUC: 0.741; threshold: 39.1 mg/L; sensitivity: 61.7%; specificity: 79.3%). SII (AUC: 0.597) and SIRI (AUC: 0.612) yielded statistically significant AUC values but showed limited discriminative ability. No significant association was found between DST and CA, whereas a weak positive correlation was found between CRP and length of hospital stay (r=0.285; p<0.001).Conclusions: SII and SIRI were significantly elevated in CA, but their diagnostic performance was lower than that of CRP. The findings suggest that moderate in-hospital delay was not associated with increased rates of CA in this cohort. Prospective studies evaluating the combined use of these indices with CRP and their integration into clinical scoring systems are needed.