© 2018 Trials within Cohorts    Contact: c.relton@qmul.ac.uk.  Supported  by  Wellcome Trust grant and the NIHR CLAHRC for Yorkshire & Humber 

This section describes the rationale for the 'cohort multiple RCT' design, how the design is being used, the different types of published protocols relating to the design. The differences between standalone trials and trials within cohorts is also explained, including a description of the different approaches to informed consent.

Rationale for the cmRCT design

The theoretical article describing the design was published in 2010. Relton C, O'Cathain A, Nicholl J, Torgerson D. Rethinking pragmatic randomised controlled trials: Introducing the "cohort multiple randomised controlled trial" design. 2010 BMJ Online 340(7753):963-967. The cmRCT design was created in an attempt to overcome many of the problems associated with standard pragmatic randomised controlled trial (RCT) design (poor recruitment rates, unrepresentative trial populations, lack of long term outcomes etc.); problems which reduce the generalisability of results and a sub-optimal system for efficiently informing routine healthcare decision making. 

Implementation of the cmRCT design

 

Since its publication, the theoretical article describing the design has been well cited, and the cmRCT design is now being used in a variety of settings and arenas.

 

The initial partial pilot of the design was conducted in 2005-2007 in a UK NHS community clinic and the trial results were published in 2012.

 

A hypothetical test of the acceptability of the design was conducted in primary care mental health in the UK.

 

In addition to conference presentations about the design, and symposiums of triallists interested in (or already using the design), triallists in a number of different fields have cited the design as a potential way forward for research in their field e.g. Verkooijen 2013. And some groups have held consensus building events e.g. stakeholders in prostate cancer surgery

Protocols using the cmRCT design

A growing number of protocols for studies using the cmRCT design are now being published in trial registries and/or in peer reviewed online journals – these include a four different types of protocols. Below are some examples of each different type.

  • Protocols describing the methods used to create long term observational studies (cohorts) with the facility for multiple trials.

  •    Examples
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  • Protocols describing the cohorts and one or more of the trials planned to be embedded within the cohort.

       Examples
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  • Protocols for RCTs  within already created cohorts

        Examples
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  • Protocols for RCTs  - which then build a cohort around the trial

        Examples