Same intervention, different opinions: some challenges of doing Study Within A Trial (SWAT) replication studies
Brighton, UK

Speaker: Anne Duncan and Kirsteen Goodman

This is a talk at the International Clinical Trials Methodology Conference (ICTMC), Brighton, UK, 6th – 9th October 2019.  Venue is the Hilton Brighton Metropole.

Parallel Session 1A – Improving Follow-Up and Retention

Authors: Anne Duncan, Suzanne Hagen, Shaun Treweek, Kirsteen Goodman


Studies Within A Trial (SWATs) provide evidence to support trial process decisions.  We will use the example of replicating the same SWAT intervention in three different trialsto illustratesome challenges (expected and unexpected) in doing SWATs.


A theoretically-informed cover letter (SWAT24) was found to improve response rates to postal questionnaires in the IQuaD dental trial by 6%.  We aimed to see if the benefits of SWAT24 were replicated in other trials.

The INTERVAL (dental), AMBER (MS) and OPAL (urinary incontinence) trials replicated SWAT24, randomising participants to receive either the theoretically informed cover letter or standard cover letter with their follow-up questionnaires.  Each trial was required to gain ethical approval, as well as buy-in from local PIs.  


Approval was given for all three trials. However, review of the same SWAT intervention led to different requirements from ethical committees to gain approval.  For OPAL, the committee thought the language coercive and requested changes  There were similar concerns from the committee handling AMBER and a local PI thought the letter would undermine relationships with participants and did not take part.  The committee handling approvals for INTERVAL thought the language aggressive. Minor changes were made to text for OPAL, AMBER and INTERVAL.  To our knowledge, none of the 1432 participants receiving the SWAT24 letter in IQuAD, INTERVAL, OPAL and AMBER raised concerns.  Meta-analysis shows a pooled increase in response rate of 4% (95% CI=0% to 8%) in favour of the theory-informed letter.


Replication is key to SWATs.  For replication evaluations of a SWAT, it would be efficient for committees and others to have sight of previous ethical judgements, as well as information on response from previous participants.  Trial Forge is working with the Health Research Authority on streamlining the approvals process for SWATs in the UK.

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