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. 2025 Feb 4:388:e080785.
doi: 10.1136/bmj-2024-080785.

Guidance for protocol content and reporting of factorial randomised trials: explanation and elaboration of the CONSORT 2010 and SPIRIT 2013 extensions

Brennan C Kahan  1 , Edmund Juszczak  2 , Elaine Beller  3 , Megan Birchenall  2 , An-Wen Chan  4 , Sophie Hall  2 , Paul Little  5 , John Fletcher  6 , Robert M Golub  7 , Beatriz Goulao  8 , Sally Hopewell  9 , Nazrul Islam  5   6 , Merrick Zwarenstein  10 , Diana Elbourne  11 , Alan Montgomery  2
Affiliations

Guidance for protocol content and reporting of factorial randomised trials: explanation and elaboration of the CONSORT 2010 and SPIRIT 2013 extensions

Brennan C Kahan et al. BMJ. .

Abstract

This report presents the explanation and elaboration paper for the CONSORT (Consolidated Standards of Reporting Trials) 2010 and SPIRIT (Standard Protocol Items: Recommendations for Interventional Trials) 2013 extensions for factorial trials. Factorial trials involve randomising participants to more than one intervention, often with the aim of evaluating multiple interventions in one study or assessing whether treatments interact. The CONSORT and SPIRIT statements have been extended to allow for the unique features of the factorial design. Reporting items along with detailed explanations and examples of good practice are provided, as well as a glossary of key terms and an overview of the methodological features of factorial trials.

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Conflict of interest statement

Competing interests: All authors have completed the ICMJE uniform disclosure form at https://www.icmje.org/disclosure-of-interest/ and declare: support from the MRC for the submitted work. SH and A-WC are members of the SPIRIT-CONSORT executive group and leading the current update of the SPIRIT 2013 and CONSORT 2010 reporting guidelines funded by the UK MRC National Institute for Health Research (NIHR) Better Methods, Better Research (MR/W020483/1). NI is paid to work as a research editor for The BMJ; during the course of the project, NI received funding from the UK Office for National Statistics (ONS) and UK NIHR unrelated to the submitted work. JF is paid to work as an associate editor for The BMJ. No other disclosures were reported. JF and NI worked for The BMJ during guideline development, but were not involved in any of the decisions regarding review of the manuscript or its acceptance. This article reflects the views of the authors, the Delphi panellists, and the consensus meeting panellists and may not represent the views of the broader stakeholder groups, the authors’ institutions, or other affiliations.

Figures

Fig 1
Fig 1
Example of a flow diagram for a factorial trial (NeoCLEAR). The NeoCLEAR trial assessed infant position and timing of stylet removal to improve lumbar puncture success in newborn babies. Figure adapted from Marshall et al. Screening and eligibility data are not shown
Fig 2
Fig 2
Example flow diagram of a factorial trial showing additional data summaries (GRASP trial). The GRASP trial compared progressive exercise (Prog Ex) with best practice advice (BPA) for patients with rotator cuff disorders. Figure adapted from Hopewell et al
See this image and copyright information in PMC

References

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    1. Chan AW, Tetzlaff JM, Gøtzsche PC, et al. SPIRIT 2013 explanation and elaboration: guidance for protocols of clinical trials. BMJ 2013;346:e7586. 10.1136/bmj.e7586 - DOI - PMC - PubMed
    1. Moher D, Hopewell S, Schulz KF, et al. CONSORT 2010 explanation and elaboration: updated guidelines for reporting parallel group randomised trials. BMJ 2010;340:c869. 10.1136/bmj.c869 - DOI - PMC - PubMed
    1. Schulz KF, Altman DG, Moher D, CONSORT Group . CONSORT 2010 statement: updated guidelines for reporting parallel group randomised trials. BMJ 2010;340:c332. 10.1136/bmj.c332. - DOI - PMC - PubMed
    1. Campbell MK, Piaggio G, Elbourne DR, Altman DG, CONSORT Group . Consort 2010 statement: extension to cluster randomised trials. BMJ 2012;345:e5661. 10.1136/bmj.e5661 - DOI - PubMed

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