Pick your certainty level
All Evidence
- 22%
A peer‐led follow‐up strategy may result in a large increase in retention.
- 20%
Giving a pen at recruitment probably increases retention.
- 13%
Randomising participants at recruitment to an open rather than a blinded trial may result in a large increase in retention.
- 10%
Addition of monetary incentives to all trial arms may favour the higher value incentive to increase retention.
- 9%
Addition of a monetary reward to both trial arms delivered either with the prenotification or with the reminder letter, probably increases retention.
- 9%
Using a self-sampling kit probably increases retention.
- 8%
Inclusion of a newspaper article about the trial may increase retention.
- 7%
Monetary incentives may increase retention.
- 6%
The addition of optimised information, either as bespoke or template formats, may increase retention.
- 6%
Frequency of telephone contact may increase retention.
- 4%
Various return postage strategies may increase retention slightly.
- 3%
Prenotification cards may increase retention slightly.
- 2%
First class postage for outward mail may increase retention slightly.
- 2%
Addition of a pen may increase retention slightly.
- 2%
Electronic prompts compared to electronic reminders may increase retention slightly.
- 1%
Electronic reminders compared to usual follow‐up may result in little or no difference to retention.
- 1%
Use of a sticker on envelope may result in little or no difference to retention.
- 0%
Addition of a post‐it note may result in little or no difference to retention.
- 0%
Inclusion of a societal benefit message may result in little or no difference to retention.
- -1%
Including a social incentive in the cover letter may result in little or no difference to retention.
- -1%
Telephone reminders compared to usual follow‐up may result in little or no difference to retention.
- -2%
Personalised prompts up may reduce retention slightly.
- -3%
Addition of a diary to usual follow-up probably reduces retention slightly.
- -19%
Telephone reminders compared to postal reminders, may result in a large decrease in retention.
Top 5 Retention Tip
01.
Offering monetary incentives may increase retention: see Cochrane review.
02.
Newsletters are widely used as a retention intervention but the evidence to support their use is of very low certainty. Evaluations of newsletter compared to no newsletter would be welcome.
03.
The Trial Forge SWAT Network intends to publish a priority list of retention intervention in need of evaluation in Studies Within A Trial (SWATs) soon. Watch this space..
04.
More to come: keep checking the site…
05.
More to come: keep checking the site…
More About Retention
Most trials involve more than one contact with a participant after they have been recruited, allowing for data collection over a pre-defined period of time. This contact comes in many forms; some examples include face-to-face meetings, through letters, the internet, telephone calls, text messaging, email or the return of medical test kits. Missing data can result from any of these data collection methods, sometimes people are too busy to reply, they have changed their mind and no longer want to participate in the study, or they may have experienced unwanted or unexpected side effects as a result of trial participation.
The attrition of trial participants can impact negatively on the trial’s results. Bias can be introduced if participants drop-out as a result of experiencing severe side effects, and the study can be underpowered if attrition rates are substantial.
