Background: Computed tomography (CT) is generally accepted as a modality of choice for imaging workup in patients with suspected appendicitis. A standardized CT reporting system, CT certainty score, has been proposed to improve diagnostic accuracy and to reduce ambiguous CT reports.

Objective: To assess the diagnostic performance and the reliability of the standardized CT reporting system for acute appendicitis in Thai adults.

Materials and Methods: The present study was a retrospective data review of 421 adult patients who had CT scans of the appendix between January 2016 and December 2017. The clinical and imaging data were extracted and analyzed. The pathological result was used as a standard of reference. The diagnostic performance and interobserver agreement of the standardized CT reporting system were estimated.

Results: One hundred sixty-three patients, with a mean age of 41.7 years, had clinical diagnoses of acute appendicitis. Using standardized CT report, radiologists were highly accurate at diagnosing appendicitis [area under curve (AUC) 0.988 (95% CI 0.98 to 1.00); p<0.001]. The estimated sensitivity, specificity, positive predictive value, negative predictive value, and accuracy were 95.1% (95% CI 90.6 to 97.9), 95.7% (95% CI 92.5 to 97.9), 93.4% (95% CI 88.7 to 96.2), 96.9% (95% CI 93.0 to 97.2), 95.5% (95% CI 93.0 to 97.3), respectively. The interobserver agreement was greater than 80% for all binary objective findings and more than 90% agreement on the presence or absence of greater-than-3-mm wall thickness, appendicolith, periappendiceal air, and right lower quadrant fluid collection. The use of CT certainty score had interobserver agreement of 78% (κ=0.69; 95% CI 0.62 to 0.77).

Conclusion: Using a standardized CT reporting system yielded a high diagnostic accuracy and high reproducibility of supportive CT findings for appendicitis in at-risk patients. The standardized CT reporting system can improve diagnostic certainty, accuracy, and guide patient management.

Keywords: Appendicitis; Certainty score; Computed tomography; Standardized reporting system

DOI: doi.org/10.35755/jmedassocthai.2021.07.12434

Received 5 February 2021 | Revised 2 June 2021 | Accepted 4 June 2021