Use of the Appendistat (APS) score to triage patients with suspected acute appendicitis: a retrospective cross-sectional study in one of the busiest UK surgical emergency units

Introduction: Although nonoperative management of acute appendicitis may be appropriate in selected cases, appendicectomy remains the gold standard treatment. Early prioritization of patients at risk of developing complicated appendicitis is important for optimizing outcomes. This study aims to assess the predictive value and clinical utility of the Appendistat (APS) scoring as a triage tool to identify patients at increased risk of complicated appendicitis. Methods: This retrospective, cross-sectional observational study included 592 patients who underwent appendicectomy. Based on their final histological diagnosis, patients were categorized as normal, acute uncomplicated appendicitis (AUA), or acute complicated appendicitis (ACA). The discriminative performance of the APS score for identifying ACA at presentation was evaluated. Results: APS scores were significantly higher in patients with ACA (median = 63%, range = 2–97%) compared with a combined comparator group of normal appendix and AUA (median = 40%, range = 1–100%; P < 0.0001). In this pragmatic clinical comparison, the APS score demonstrated moderate discriminative performance, with an area under the receiver operating characteristic curve of 0.71 (95% CI = 0.65, 0.76). Using a predefined APS score cutoff value of 40%, sensitivity for identifying patients with ACA was 79% (95% CI = 71, 85); specificity was 51% (95% CI = 46, 56); and positive and negative predictive values were 35% and 83%, respectively. Conclusion: The APS score is a safe and readily available triage tool that supports early risk stratification in patients presenting with acute appendicitis. An APS cutoff of 40% identifies patients at risk of complicated appendicitis and may assist in prioritizing urgent surgical intervention when used alongside clinical assessment.