Validation of the paediatric appendicitis risk calculator (pARC) in an Australian emergency department setting

Our objective is to assess the performance of the Paediatric Appendicitis risk calculator (pARC) in quantifying the risk of appendicitis, in an Australian tertiary emergency department (ED) and to compare its performance with that of the Paediatric Appendicitis Score (PAS) and Alvarado score in predicting risk of appendicitis. We conducted this prospective, observational cohort study from July 2021 to October 2022 in the Women's and Children's Hospital (WCH) ED in Adelaide, South Australia. Patients aged 5 to 18 presenting with abdominal pain ≤120 h, where appendicitis was a differential diagnosis, were eligible for enrolment. Our primary outcome was the histopathological diagnosis of appendicitis within 14 days of initial presentation. We reported performance characteristics and secondary outcomes by pARC risk strata and compared the receiver operator characteristic (ROC) curves of the PAS, Alvarado and pARC. We enrolled 675 patients with a mean age of 11.93 years, 51 % were female. Appendicitis was histologically diagnosed in 29.33 % of patients, with 13.6 % having perforated appendicitis. 51 % of patients had very low (<5 %) or low (5 % to 14 %) predicted risk, 40.3 % had intermediate risk (15 % to 84 %), and 6.5 % had high risk (>85 %). In the very-low- and low-risk groups, 6.4 % and 11 % of patients had appendicitis, respectively. The AUROC was 0.852 (95 % confidence interval (CI) 0.820 to 0.885) for the pARC compared with 0.80 (95 % CI 0.77 to 0.84) for the PAS, and 0.73 (95 % CI 0.69, 0.78) for Alvarado. The pARC score has been validated as an appendicitis risk calculator which is as reliable as previous studies, in the study population, whilst outperforming the PAS and Alvarado scores.