Validation of the APPEND clinical decision tool for the diagnosis of acute appendicitis

Background: The APPEND score is a clinical decision tool (CDT) for stratifying the risk of patients presenting with right lower quadrant (RLQ) abdominal pain having acute appendicitis. The aim of this study was to validate the APPEND score in an Australian metropolitan hospital population. Methods: A retrospective review of consecutive patients from January to December 2024 at least 16 years of age that were referred to the general surgery service with acute RLQ pain in an Australian metropolitan hospital. The diagnostic properties including sensitivity, specificities, positive predictive value (PPV), negative predictive values (NPV) and area under the curve (AUC) of the APPEND score were assessed and then compared with the Alvarado score. Agreement between the scores were also assessed. Results: Of the 229 patients referred for acute RLQ pain, the APPEND score demonstrated high sensitivity of 98% in the low risk group identified with a score of 1 or less and a PPV of 100% in the high risk group (APPEND score ≥5. It has good agreement with the Alvarado score when identifying the low risk group (p=1) but low agreement when identifying the high risk group (p<0.001). The AUC was reasonable at 0.746 compared to the 0.823, p=0.02. Conclusions: The APPEND score shows promise as a CDT for acute appendicitis in Australian metropolitan populations, potentially reducing negative appendectomy rates and radiological resources. While the APPEND score offers simplicity and strong performance, further multicenter validation is crucial before widespread clinical adoption in Australia.