Abstract:Background: Preoperative diagnosis of acute appendicitis is classically a clinical one, but with the increasing use of technology for arriving at a fool proof diagnosis, surgeons rely on radiology to a considerable extent for decision making. Especially, in developing countries where time and resources are limited, a reliable Ultrasonography (USG) based score for diagnosing acute appendicitis improves decision making. This prospective study was carried out to compare Modified Alvarado Score & Tzanakis's Score for diagnosing acute appendicitis. Methods: 146 patients undergoing emergency appendectomy for suspected acute appendicitis were included in the study. This was a prospective study carried out from July 2014 to March 2016. Patients included in the study were scored according to Modified Alvarado Score (MAS) and Tzanakis Score (TS). The final diagnosis was confirmed by histopathology. Results: The sensitivity, specificity, positive predictive value, negative predictive value and likelihood ratio of MAS were 94.95%, 92.6%, 98.26%, 80.64% and 0.05 respectively, and of TS were 98.32%, 96.29%, 99%, 92.85% and 0.02 respectively. Negative appendectomy rate was 1.74% for MAS (cutoff ≥7) and 0.84% for TS (cutoff ≥8). Overall negative appendectomy rate was 18.5%. Conclusion: Tzanakis score is simple, applicable and effective for diagnosing acute appendicitis.