PurposeAcute appendicitis (AA) is one of the most common causes of an acute abdomen. The accuracies of the Alvarado and the acute inflammatory response (AIR) scores in the diagnosis of appendicitis is very low in Asian populations, so a new scoring system, the Raja Isteri Pengiran Anak Saleha Appendicitis (RIPASA) system, was designed recently. We applied and compared the Alvarado, AIR, and RIPASA scores in the diagnoses of appendicitis in the Iranian population.MethodsWe prospectively compared the RIPASA, Alvarado, and AIR systems by applying them to 100 patients. All the scores were calculated for patients who presented with right quadrant pain. Appendectomies were performed; then, the postoperative pathology reports were correlated with the scores. Scores of 8, 7, and 5 or more are optimal cutoffs for the RIPASA, Alvarado, and AIR scoring systems, respectively. The sensitivities, specificities, positive predictive values, negative predictive values (NPVs), positive and negative likelihood ratios (LRs) for the 3 systems were determined.ResultsThe sensitivity and the specificity of the RIPASA score were 93.18% and 91.67%, respectively. The sensitivities of the Alvarado and the AIR scores were both 78.41%. The specificities of the Alvarado and the AIR scores were 100% and 91.67%, respectively. The RIPASA score correctly classified 93% of all patients confirmed with histological AA compared with 78.41% for the Alvarado and the AIR scores.ConclusionThe RIPASA scoring system had more sensitivity, better NPV, a positive LR, and a less negative LR for the Iranian population whereas the Alvarado scoring system was more specific.