Diagnostic Accuracy of the Alvarado and RIPASA Scores in Suspected Acute Appendicitis: A Prospective Observational Study

Background: Acute appendicitis is a common cause of acute abdominal pain requiring prompt surgical intervention. Accurate diagnosis remains challenging, particularly in populations with atypical presentations. This study aims to compare the diagnostic accuracy of the Alvarado and RIPASA scoring systems in an Iranian cohort. Methods: A prospective observational study was conducted in the emergency departments of two hospitals in Tehran, involving 340 patients suspected of having acute appendicitis. Both Alvarado and RIPASA scores were calculated, and their diagnostic performance was compared using post-operative histopathological findings as the gold standard. Results: Acute appendicitis was confirmed in 312/340 (91.8%) participants. The RIPASA score demonstrated superior diagnostic accuracy compared to the Alvarado score, with a sensitivity of 85% versus 57% and an overall diagnostic accuracy of 85% versus 60%. The specificity was comparable between the two scores, with the Alvarado at 89% and the RIPASA at 86%. The RIPASA score also had a higher negative predictive value (34% vs. 18%) and positive likelihood ratio (6.07 vs. 5.18). Conclusions: In this high-prevalence cohort of ED patients evaluated for suspected appendicitis, the RIPASA score showed higher sensitivity and overall diagnostic accuracy than the Alvarado score. However, given the selected study population and the verification strategy, external validity to unselected ED populations may be limited; multicenter studies using a uniform reference standard for both operated and non-operated patients are warranted.