LOCAT (low-dose computed tomography for appendicitis trial) comparing clinical outcomes following low- vs standard-dose computed tomography as the first-line imaging test in adolescents and young adults with suspected acute appendicitis: Study protocol for a randomized controlled trial

Soyeon Ahn, Sang Hoon Cha, Han Jin Cho, Jea Min Cho, Seong Whi Cho, Pil Cho Choi, Sung Hyuk Choi, Yoo Shin Choi, Yong Hwan Chung, Bon Seung Gu, Young Rock Ha, Sang Kuk Han, Jae Yeon Heo, Seong Sook Hong, Suk Ki Jang, Sung Bum Kang, Bohyoung Kim, Cho Hee Kim, Ho Jung Kim, Hyuk Jung KimJoong Hee Kim, Kwang Pyo Kim, Kyuseok Kim, Mi Kyung Kim, Mi Sung Kim, Min Jeong Kim, Sung Eun Kim, Young Chul Kim, Young Hoon Kim, Yousun Ko, Heon Ju Kwon, Chang-Hee Lee, Hae Kyung Lee, Hye Seung Lee, Jae Hyuk Lee, Ji Eun Lee, Jongmee Lee, Kyoung Ho Lee, Min Hee Lee, Min Jung Lee, Yoon Jin Lee, Ri Young Na, Chan Jong Park, Chul Woo Park, Ji Hoon Park, Sung Bin Park, Yang Shin Park, Dong Hyuk Shin, Eun Jung Shin, Hyun Sik Woo, Ji Young Woo, Hyun Kyung Yang, Suk Keu Yeom, Boem Ha Yi

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20 Citations (Scopus)


Background: Computed tomography is widely used to diagnose acute appendicitis. Many adolescents and young adults are exposed to the associated radiation. A recent single-institution trial has reported promising results for low-dose computed tomography; however, this technique has not yet been widely adopted. LOCAT (low-dose computed tomography for appendicitis trial), a multi-institution randomized controlled non-inferiority trial, aims to compare low-dose computed tomography and standard-dose computed tomography as the first-line imaging tests for adolescents and young adults, and therefore to test the generalizability of the previous single-institution trial results.Methods/Design: Participants with suspected appendicitis are randomly assigned to either the low-dose group (with a typical effective dose of 2 mSv) or the standard-dose group (as used in normal practice at each participating site, typically 8 mSv). The primary end point is the negative appendectomy rate (the percentage of the number of uninflamed appendices that were removed among all non-incidental appendectomies), which is a consequence of false-positive diagnoses, with a non-inferiority margin of 4.5 percentage points. The key secondary end point is the appendiceal perforation rate, which is a consequence of delayed (or false-negative) diagnoses. Participant recruitment will be continued until the number of non-incidental appendectomies for each group exceeds 444. The total number of expected participants approximates 3,000, including those not undergoing appendectomy.Discussion: In addition to the study protocol, we elaborate on several challenging or potentially debatable components of the study design, including the broad eligibility criteria, choice of the primary end point, potential effect of using advanced imaging techniques on study results, determining and adjusting the radiation doses, ambiguities in reference standards, rationale for the non-inferiority margin, use of the intention-to-treat approach and difficulties in defining adverse events.Trial registration: ClinicalTrials.gov NCT01925014.

Original languageEnglish
Article number28
Issue number1
Publication statusPublished - 2014 Jan 17



  • Appendicitis
  • Radiation
  • Tomography
  • X-ray computed

ASJC Scopus subject areas

  • Medicine (miscellaneous)
  • Pharmacology (medical)

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