Low-dose CT for appendicitis appears noninferior to standard-dose CT

Patients with suspected appendicitis at 20 South Korean teaching hospitals were randomly assigned to receive low-dose CT (2 mSv) or standard-dose CT (3 to 8 mSv).

Low-dose appendiceal CT can be performed in adolescents and young adults without affecting the negative appendectomy rate, appendiceal perforation rate, and other clinical outcomes, a study found.

To compare the effectiveness of low-dose CT and standard-dose CT for diagnosing appendicitis in adolescents and young adults, researchers conducted a pragmatic, randomized controlled noninferiority trial at 20 South Korean teaching hospitals that had little experience with low-dose CT. Patients 15 to 44 years of age with suspected appendicitis were randomly assigned 1:1 to receive low-dose CT (2 mSv) or standard-dose CT (3 to 8 mSv). The primary endpoint was the rate of negative or unnecessary appendectomy, an indicator of false-positive diagnosis, among all appendectomies, with a noninferiority margin of 4.5% for low-dose versus standard-dose CT.

Results were published online Sept. 11 by The Lancet Gastroenterology & Hepatology.

Researchers assigned 1,535 patients to the low-dose CT group and 1,539 patients to the standard-dose CT group. Of these, 559 and 601 patients, respectively, went on to have appendectomies. Twenty-two of 559 patients in the low-dose group (3.9%) had a negative appendectomy versus 16 of 601 patients (2.7%) in the standard-dose group (difference, 1.3%; 95% CI, −0.8% to 3.3%; P=0.0022 for the noninferiority test). The two groups were also similar for endpoints related to false-negative (or delayed) diagnosis, including appendiceal perforation rate, prevalence of perforated appendicitis, interval between CT and appendectomy, hospital stay associated with appendectomy, and diagnostic sensitivity.

There were 43 adverse events in 43 of 1,535 patients (2.8%) in the low-dose group and 41 adverse events in 40 of 1,539 patients (2.6%) in the standard-dose group. One life-threatening adverse event, anaphylaxis caused by an iodinated contrast material, occurred in the low-dose group.

The authors wrote that a radiation dose of 2 mSv is similar to the worldwide average annual exposure to natural radiation sources or the dose of three conventional abdominal radiographs. In view of the vast number of appendiceal CT examinations done worldwide, use of low-dose CT could prevent a sizeable number of radiation-associated cancers in the future, the researchers wrote.

“These results should not be interpreted as an encouragement to increase use of CT by introducing the low-dose technique,” the authors wrote. “A successful reduction of population radiation dose should entail judicious CT use and dose lowering in individual examinations.”

An accompanying comment noted that obesity may be a complicating factor in using low-dose CT but continued, “Because low-dose CT protocols for suspected acute appendicitis are not inferior to standard CT, they should be implemented in all emergency departments according to the as-low-as-reasonably-achievable principle, to enable substantial reduction in radiation doses for patients with suspected appendicitis.”