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.

Abstract

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.