Comparing the diagnostic accuracy of modified RIPASA and MASS in patients diagnosed with acute appendicitis in Suez Canal University Hospital Emergency Department: a cross-sectional study
Authors: Moussa Bassant Sayed , Ali Mohamed Amin , Mohamed Dina AbdulRahman Ramadan , Shahhat Amal Mohamed El 
Published: August 2022

Abstract
Introduction
Acute appendicitis is the most common surgical condition presented in emergency departments globally. It is also the most common cause of abdominal pain treated surgically, with a lifetime risk of 7%. Recent studies show MASS to be easy, simple and cheap diagnostic tool for supporting the diagnosis of acute appendicitis.The modified RIPASA scoring system includes more parameters than MASS and the latter did not contain certain parameters. These parameters are shown to add to the accuracy of modified RIPASA over MASS especially in Asian population.

Aim of this study
The aim of the study was to improve the diagnosis of acute appendicitis in order to lower the negative appendectomy rates.

Patients & methods
This is cross sectional study, the study included 40 patients presented to the emergency department at Suez Canal University hospital with abdominal pain and suspected clinically as acute appendicitis. Then the decision of surgical intervention was made by surgeons, who were blinded for our study, based on their clinical judgment. Then both scores were calculated for all patients and other clinical data were obtained from patients after accepting being included in our study with an informed consent.After operations, the operating theatre records were obtained and cases pathological investigation of the appendices was done. Then the sensitivity, specificity, positive and negative predictive values were calculated and so the diagnostic accuracy for both scoring systems.

Results
Clinically, all the patients were suffering acute right iliac fossa tenderness (100%), rebound tenderness (90%), and nausea/ vomiting (70%). Only 45% had elevated White blood count and 55% had negative urine analysis.
Histopathological analysis of appendices of the studied patients showed that 40% of the patients had suppurative appendicitis, one quarter of them had catarrhal appendicitis and only 20% had complicated perforated appendicitis. Meanwhile, about 15% had normal (negative) appendix. Modified RIPASA showed a good discriminative ability in our study where the area under the curve for modified RIPASA was 0.902 (95% CI: 0.798 – 1.00) (p = 0.002). Moreover, a value of 8.5 or higher was found to be the best cut-off point to predict acute appendicitis among patient suspected clinically as acute appendicitis with sensitivity = 70.6%, specificity = 100%, positive predictive value of 100%, and negative predictive value of 37.5% and 75% accuracy.The best cut-off score to diagnose acute appendicitis in our sample based on MASS was fixed at 5.5, where the sensitivity of the MASS reached 47.1%, with specificity of 33.3%, positive predictive value of 80%, negative predictive value of 10% and accuracy 45%.

Conclusion
The modified RIPASA score is the best diagnostic scoring system for acute appendicitis if compared to the modified Alvarado score, with the former achieving significantly higher sensitivity and diagnostic accuracy. Modified RIPASA was concluded to be a more applicable and useful score. Negative appendicectomy rates can also be avoided by using modified RIPASA score.