• Suvi Sippola, Johanna Virtanen, Ville Tammilehto, Juha Grönroos, Saija Hurme, Hannele Niiniviita, Elina Lietzen, and Paulina Salminen.
• Division of Digestive Surgery and Urology, Turku University Hospital, Turku, Finland.
• Ann. Surg. 2020 Feb 1; 271 (2): 332-338.

ObjectiveTo compare diagnostic accuracy of contrast enhanced low-dose computed tomography (CT) accomplished in the OPTICAP trial phantom phase to standard CT in patients with suspected acute appendicitis.BackgroundIncreasing use of CT as the gold standard in diagnosing acute appendicitis has raised concerns regarding radiation exposure. Unenhanced low-dose CT protocols have shown similar diagnostic accuracy with standard CT for diagnosing appendicitis. To our knowledge, there are no other trials in which the same patient with suspected acute appendicitis underwent both standard and low-dose CT allowing interpatient comparison.MethodsOPTICAP is an interpatient protocol sequence randomized noninferiority single-center trial performed at Turku University Hospital between November, 2015 and August, 2016. Sixty patients with suspected acute appendicitis and body mass index <30 kg/m were enrolled to undergo both standard and low-dose contrast enhanced CT scans, which were categorized as normal, uncomplicated or complicated appendicitis by 2 radiologists in blinded manner. All patients with CT confirmed appendicitis underwent appendectomy to obtain histopathology.ResultsThe low-dose protocol was not inferior to standard protocol in terms of diagnostic accuracy; 79% [95% confidence interval (CI) 66%-89%) accurate diagnosis in low-dose and 80% (95% CI 67%-90%) in standard CT by primary radiologist. Accuracy to categorize appendicitis severity was 79% for both protocols. The mean radiation dose of low-dose CT was significantly lower compared with standard CT (3.33 and 4.44 mSv, respectively).ConclusionDiagnostic accuracy of contrast enhanced low-dose CT was not inferior to standard CT in diagnosing acute appendicitis or distinguishing between uncomplicated and complicated acute appendicitis in patients with a high likelihood of acute appendicitis. Low-dose CT enabled significant radiation dose reduction.

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