Creating Optimal Reporting Methods for Factorial Randomized Trials


Recent study proposes consensus-based extension to the Consolidated Standards of Reporting Trials 2010 Statement for factorial trials.

Image Credit: © Tierney -

Image Credit: © Tierney -

In a study recently published in JAMA, the authors sought to address the current suboptimal reporting of factorial trials. “Transparent reporting of randomized trials is essential to facilitate critical appraisal and interpretation of results,” the authors wrote. “Factorial trials, in which 2 or more interventions are assessed in the same set of participants, have unique methodological considerations.”1

The article presents an extension to the Consolidated Standards of Reporting Trials (CONSORT) 2010 Statement for the reporting of factorial trials. The extension, developed through a systematic process, modifies 16 items from the CONSORT 2010 checklist and introduces 1 new item.1

According to the Enhancing the Quality and Transparency of Health Research (EQUATOR) Network, “The CONSORT Statement is an evidence-based, minimum set of recommendations for reporting randomized trials. It offers a standard way for authors to prepare reports of trial findings, facilitating their complete and transparent reporting, and aiding their critical appraisal and interpretation. It comprises a 25-item checklist and a flow diagram. The checklist items focus on reporting how the trial was designed, analyzed, and interpreted; the flow diagram displays the progress of all participants through the trial.”

The CONSORT statement has been endorsed by prominent medical journals and leading editorial organizations.2

The CONSORT extension was developed by using the EQUATOR methodological framework. The authors generated a list of reporting recommendations for factorial trials using a scoping review of methodological articles, utilized a 3-round Delphi survey to identify additional items and assess the importance of each item, and held a hybrid consensus meeting to finalize the selection and wording of items for the checklist.1

The 16 modified elements included an emphasis on clarifying the use of factorial trials. Some of the changes listed were: identification as a factorial randomized trial in the title of the work, rationale for using a factorial design, a statement of which treatment groups form the main comparisons, description of the type of factorial trial, and eligibility criteria for each factor. There were also elements that called for increased clarification on trial design elements, such as recruitment and outcome assessments.1

Finally, the new element introduced by the authors, “Participant flow, losses and exclusions, and outcome data (including primary and secondary outcomes, harms, and adherence) presented by treatment groups,” calls for additional data summaries in factorial trials.1

“This extension to the CONSORT 2010 Statement provides guidance for reporting factorial trials, the authors wrote. “The extension checklist represents the minimum essential requirements for reporting of factorial trials; for some trials there will be additional items that are important to report. For instance, if primary or secondary outcomes differ by factor, this should be reported. Similarly, if multiple testing is deemed to be an issue, authors should report how this was handled.”1

While the extension provides more clarity on the reporting of factorial trials, there are limitations. Being that it was developed for studies in which results for each factor would be published simultaneously in the same article, this level of reporting may not always be feasible. Also, the Delphi survey utilized may not represent the views of all individuals because respondents were self-selecting and consensus meeting panelists were purposively identified based on their expertise.1


  1. Kahan BC, Hall SS, Beller EM, et al. Reporting of Factorial Randomized Trials: Extension of the CONSORT 2010 Statement. JAMA. 2023;330(21):2106–2114. doi:10.1001/jama.2023.19793
  2. Good Reports. (n.d.). CONSORT Statement. Good Reports.,their%20critical%20appraisal%20and%20interpretation
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