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Writing treatment effect as ‘twice as fast’ rather than ‘half as fast’ may improve recruitment.
Opt‐out consent may improve recruitment.
Enclosing a questionnaire covering issues relevant to trial with the invitation probably increases recruitment.
Having an open rather than a blinded placebo trial increases recruitment.
Telephone reminders probably increase recruitment.
Financial incentives probably increase recruitment slightly.
Giving quotes from existing participants in text messages probably increases recruitment slightly.
Mentioning scarcity of trial places in text messages probably increases recruitment slightly.
Optimising the participant information leaflet (PIL) through a particular, bespoke process involving formal user testing makes little or no difference to recruitment.
Email invitations probably result in little to no difference in recruitment compared to postal invitations but is cheaper to use.
Recruitment at a church and other enhancements may improve recruitment.
Brief PILs make little or no difference to recruitment.
An enhanced recruitment package including more contact by telephone may make little or no difference in recruitment.
Sending a recruitment primer letter may have little or no effect on recruitment.
Using a postcard teaser campaign made little or no difference to recruitment.
Optimising the PIL through using user feedback probably makes little or no difference in recruitment.
An enhanced recruitment package including more contact may make little or no difference in recruitment.
Emphasising risk in information may make little or no difference to recruitment.
A patient preference design increased total participation but made little or no difference to recruitment to the randomised trial.
Providing information over the telephone may have little or no effect on recruitment.
Internet‐based, electronic data collection compared to paper‐based may reduce recruitment.
Emphasising pain in information may reduce recruitment.
Top 5 Recruitment Tips
Opt-out, rather than opt-in, procedures may improve recruitment where it can be done. There’s only one evaluation so replication studies would be useful.
Having an open, rather than a blinded trial improves recruitment. The downside is that lack of blinding brings its own problems with outcome assessment.
Telephone reminders to non-responders. Decent evidence but in trials with very low initial recruitment. Replication studies would help.
Enclosing a questionnaire covering issues relevant to the trial together with the invitation. Only one evaluation so replication would be useful.
Financial incentives. Odds-on that this is effective but some inconsistency in effect. Replication needed.
More About Recruitment
Trials across the world struggle to recruit sufficient participants in the timescale originally defined for recruitment activity. This can result in recruitment time extensions and/or extensions to the trial budget; it is important to note that an extension denoted strictly to time is not necessarily a ‘free’ extension and may result in opportunity lost costs for the trial team and units involved. Trial extensions may delay the availability of beneficial interventions to the public, or could result in harmful or useless interventions being used for longer time periods than is ethically necessary.
If recruitment fails to successfully reach the target sample size, the likelihood of finding no statistically significant difference between outcomes where one does in fact exist, is heightened; this is referred to as a type II error.
In the worst cases trials can be abandoned as a result of poor recruitment, costing large amounts of money and leaving the research question unanswered.
Trial Forge is actively working on improving the evidence base around recruitment of trial participants; if you would like to collaborate on an embedded study focussed on recruitment strategies please get in touch.
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