Evaluating the Diagnostic Accuracy of the Alvarado Score and Abdominal Ultrasound for Acute Appendicitis: A Retrospective Single-Center Study

Background: Acute appendicitis is a complex diagnosis that often requires both clinical and radiological evaluation. Significant variations in diagnostic approaches are evident among clinicians and healthcare institutions. While certain guidelines advocate for risk stratification based on clinical characteristics, others emphasize the importance of pre-operative imaging. This study seeks to explore the accuracy of the Alvarado Score and abdominal ultrasound (AUS) in diagnosing acute appendicitis. Methods: Suspected cases of appendicitis admitted to Al-Thora Hospital in Ibb, Yemen, from Jan 2021 to July 2022 were evaluated. The demographics, clinical, and laboratory data were collected and analyzed. This study assessed Alvarado scores (calculated based on clinical evaluation and laboratory data) and pre-operative AUS findings, correlating them with post-operative and histopathology findings. The Alvarado scores and AUS sensitivity, specificity, accuracy, positive predictive value (PPV), and negative predictive value (NPV) were assessed using the ROC curve. Results: Out of 1021 cases of acute abdomen, 171 patients were suspected of appendicitis. Using AUS along with the Alvarado score, appendicitis was presumed in 137 patients who underwent appendectomy. 130 (94.9%) patients had positive intraoperative and histopathology findings while 7 (5.1%) had negative findings. The Alvarado Score had a sensitivity and specificity of 94.62% and 87.80% at cutoffs of 6, respectively Area under the curve (AUC): 0.985; 95% confidence interval (CI), 0.954 to 0.998; p < 0.0001. Abdominal US showed a sensitivity of 98.46% and specificity of 82.93% (AUC:0.907; 95% CI, 0.853 to 0.946; p < 0.0001). Conclusion: Alvarado's score and AUS exhibited high sensitivity and specificity in diagnosing acute appendicitis. The substantial accuracy and efficacy of both the Alvarado score and AUS support their utilization as primary investigative tools in resource-limited settings. This approach can help avoid unnecessary appendectomies and minimize the financial burden on patients. Plain Language Summary: Acute appendicitis poses a diagnostic challenge, with a high rate of false-positive cases identified post-operatively. Computed tomography has been recommended by several surgical societies; however, it is limited by unaffordability and unavailability. Herein, we utilized the Alvarado score along with abdominal ultrasound as an alternative accurate, and cost-effective diagnostic approach. In this study, the negative appendectomy rate was 5.1%. The sensitivity of abdominal ultrasound in detecting appendicitis was 98.5%, with a specificity of 82.9%. The positive predictive value, negative predictive value, and accuracy were determined to be 94.8%, 94.4%, and 94.7%, respectively. The mean Alvarado score was 6.9± 2.4, with a sensitivity and specificity of 97.81% and 97.06% at cutoffs of 6, respectively. The area under the curve values of the ROC curve for Alvarado's and abdominal ultrasound were 0.985 (95% CI, 0.954 to 0.998) and (AUC:0.907; 95% CI, 0.853 to 0.946), which was statistically significant (p < 0.0001). Keywords: Acute appendicitis, Alvarado's score, sensitivity, specificity, ultrasound