What is it?
Sending potential participants an email invitation to take part in a trial.
Does it work?
Email invitations probably result in little to no difference in recruitment compared to postal invitations but are cheaper to use.
How big is the effect?
An increase of 1% (95% confidence interval = -3% to 4%).
How certain are we?
GRADE Moderate certainty.
We recommend that trialists consider using email invitations when it is known that email is widely used by potential participants.
How can I use this straight away?
See Resource bundle below for details of how to use email invitations or build a SWAT evaluation of them into your trial.
Imagine a trial that needs to recruit 30 participants and initial recruitment is 30% of those approached. This means you’d need to approach 100 people to recruit 30 of them (see chart).
Now imagine using email invitations. The chart below shows the impact of an absolute increase of 1% (95% CI = -3% to 4%). Recruitment is now 31%, which means our best estimate is that 97 people would now need to be approached to recruit 30 of them.
How to Cite
Citation: Treweek S, Bruhn H, Gardner H. Evidence pack– Recruitment: Email invitations (Rec9), 2021, https://www.trialforge.org/recruitment-sector/email-rather-than-postal-invitations/.
- This summary is from the Cochrane review of strategies to improve recruitment in randomised trials (https://doi.org/10.1002/14651858.MR000013.pub6).
- It was prepared with financial support from Evidence Synthesis Ireland.
- The ‘Does it work?’ statement is structured according to effect size and GRADE certainty as per GRADE Guidelines 26 (https://doi.org/10.1016/j.jclinepi.2019.10.014). The statement is for a trivial, small unimportant or no effect size and GRADE moderate certainty.
- The recommendation statement is the consensus view of the authors of this summary based on the GRADE certainty and features of the trials contributing to the evidence.
- If you have any questions contact email@example.com.