CT based Acute Appendicitis Severity Index for acute appendicitis and validate its effectiveness in predicting complicated appendicitis

Aim To propose a CT-based scoring system called Acute Appendicitis Severity Index (AASI) for diagnosis of acute appendicitis and validates its effectiveness in predicting complicated appendicitis. Subjects and methods Retrospective analyses of CT images of 120 adult patients with pathologically proven uncomplicated (n = 64) and complicated (n = 56) acute appendicitis were performed. All patients had undergone a CT scan of the abdomen and pelvis using 320 multi-detectors computed tomography with Adaptive Iterative Dose Reduction 3D (AIDR 3D). CT image parameters were identified and used to develop a CT-based scoring system (AASI) to predict the severity of acute appendicitis and its outcome. All image analysis was performed by 2 radiologists and the total score was assigned to each patient based on the proposed CT scoring system. Validation of the effectiveness of the proposed scoring system (AASI) was done using statistical models. Results The mean and standard deviation of AASI was found to be significantly higher (P value = 0.001) in the complicated appendicitis group (observer 1 = 10.2 +/- 1.6 and observer 2 = 9.63 +/- 2.3) as compared to that in uncomplicated acute appendicitis group (observer 1 = 7.09 +/- 2.2 and observer 2 = 6.38 +/- 1.9). There was an excellent interobserver agreement of the Acute Appendicitis Severity Index for both the uncomplicated and complicated appendicitis groups (K = 0.89, 95% CI = 0.87-0.92, P = 0.001). The cutoff value for AASI used to predict complicated appendicitis was taken as 9.5 and 8.5. This resulted in an AUC of 0.877 and 0.848, accuracy of 83% and 81%, the sensitivity of 75% and 80%, the specificity of 90% and 81%, the positive predictive value of 87% and 78%, and a negative predictive value of 81% and 83% by both reviewers respectively. Conclusion The proposed CT-based AASI is a reliable parameter for the prediction of complicated appendicitis.