Accessibility statement

Trial Forge Studies Within A Trial (SWAT) Centre

Randomised controlled trials are the fairest tests for healthcare treatments, and aim to improve the health and wellbeing of people worldwide. However, there is very little evidence about how to design, deliver and report these trials.

York Trials Unit is a Trial Forge Studies Within a Trial (SWATs) Centre. Our Trial Forge SWAT Centre is part of the Trial Forge initiative, which aims to increase the evidence base for trial decision making and, in doing so, to improve trial efficiency and reduce waste in research. Our centre focuses on improving trial efficiency using a SWAT approach. More information about our SWATs programme is outlined below. Further information about the Trial Forge Initiative can be found here.

What is a SWAT?

A Study Within A Trial (SWAT) is a methodological study which aims to generate new knowledge to improve the design and delivery of future trials. Also known as a ‘nested trial’, ‘embedded trial’, or ‘trial within a trial’ a SWAT is a type of study in which an intervention to improve the conduct of a trial is tested in the context of an ongoing trial. This test of effectiveness using a trial conducted in the context of an ongoing trial forms the most rigorous evaluation of such interventions. SWATs can be randomised trials themselves (i.e. trial within a trial) or non-randomised evaluations, such as comparing electronic data collection methods alongside existing paper based data collection.

SWAT Resources and Collaboration

The Trial Forge SWAT Centre team provide ongoing support to research teams at all stages of embedding a SWAT at no cost to teams. Support includes:

  • Protocol development
  • Research ethics application advice
  • SWAT intervention selection

If you're interested in collaborating with the York Trial Forge SWAT Centre, please fill out our collaboration request form. This will help us better understand your project and determine how we can work together effectively. We look forward to hearing from you

Resources (animations and guidance documents) on the key components of the design and delivery of SWATs are now available.

SWAT Resources 

We have developed a priority list of recruitment and retention strategies to test using randomised SWATs.

Prioritised lists of recruitment and retention strategies (PDF , 546kb)

If you have any questions regarding these priorities please email us at and we will be happy to help.

Templates and text for protocols, ethics applications and example publications are available. Please contact the team at: for further information

About YTU's programme of SWATs

Our programme of SWATs aims to add to the evidence base for trial methodology, particularly the conduct and delivery of trials through the successful recruitment and retention of trial participants. Our overall ambition is to generate evidence to ensure the timely delivery of trials in order to improve the health of patients.

If you are starting a trial, please consider embedding your own SWAT to test the effectiveness of any ideas you have about improving recruitment, retention or the conduct of the trial. We are also keen to collaborate with others to test our ideas, so please consider testing one of our interventions below.

Ongoing Programmes


Funded through an NIHR Advanced Fellowship, IMPLEMENT SWATs is a ten-year programme that aims to use implementation science and SWATs to improve evidence-informed participant recruitment and retention in trials. The overarching ambition is to facilitate better methods, for better research, for better health care and better health.

Find out about the implement SWATs programme

Trial Forge SWAT Network

The 'Trial Forge SWAT Network’ aims to bring groups together that are conducting SWATs so that the evidence base can be increased more efficiently, results disseminated, and SWAT research priorities identified. In collaboration with Professor Treweek, the PROMETHEUS group at York has agreed to become the York Trial Forge SWAT centre to continue SWAT work.

The Trial Forge SWAT Network members are currently working on improvements to four key

  • SWAT priorities and evidence gaps
  • SWAT funding
  • SWAT Resources
  • SWAT repository

For more information, please see the Trial Forge SWAT Network website.

We are looking for network members so if you are interested please get in touch ( and

Completed Programmes


The aim of this programme is to pump prime existing trial teams up to £5,000 to test commonly used strategies for improving trial recruitment and retention by embedding RCTs within already funded trials. The ultimate goal is to make the inclusion of Studies Within A Trial (SWATs) routine when conducting a trial.

More information


This project aims to develop and pilot test a short training course for staff recruiting participants into surgical trials.

More information

Ongoing SWATs which are testing recruitment interventions

Objective: To evaluate the effects of adding a pen printed with the trial logo to the trial invitation.


Ongoing SWATs evaluating retention interventions

Objective: To evaluate the effectiveness of a personalised text message versus a standard text message for promoting response to postal follow-up questionnaires.

Objective: To evaluate whether SMS text messages sent as pre- or post-notification reminders improve questionnaire response rates during the follow-up for a randomised trial.

Completed SWATs to improve data collection methods

Registering and reporting SWATs

Below we list some resources which we hope you might find useful:

This is a reporting checklist for embedded recruitment trials, based on the Consolidated Standards for Reporting Trials (CONSORT) statement 2010.

This is hosted by the Northern Ireland Methodology Hub and contains outlines for more than 60 SWATs, highlighting trial processes about which there is sufficient uncertainty to justify research to improve future decision making and choice about trial design.

This project aims to bring together published and ongoing work in the field of recruitment research into a searchable database.

START aims to improve the evidence-base concerning recruitment to trials, enhance recruitment rates and make research more accessible to the public.



This project is funded by the Medical Research Council (MRC).

Grant number: MR/R013748/1


This project is funded by The Wellcome Trust through the Centre for Future Health (CFH) at the University of York.

Ref: 204829

Medical Research Council Logo SWATs

Wellcome Trust Logo TRIALISt SWATs

Contact details

Laura Clark
University of York

Contact details

Dr Adwoa Parker
University of York

Tel: 01904 32(1671)

Contact details

Trial Forge SWAT Centre
University of York

Follow us on Twitter