Skip to main content
. 2021 Mar 6;2021(3):MR000032. doi: 10.1002/14651858.MR000032.pub3

Summary of findings 12. Non‐monetary incentives: addition of pen vs usual follow‐up.

Pen compared with no pen for trial retention
Patient or population: trial participants being followed up for data collection
Settings: any setting
Intervention: pen
Comparison: no pen
Outcomes Illustrative comparative risks* (95% CI) Relative effect
(95% CI) No of Participants
(studies) Certainty of the evidence
(GRADE)
Assumed risk Corresponding risk
Pen No pen
Retention
[follow‐up]
Lowa RR 1.02 (1.00 to 1.05) 13013
(5) ⊕⊕⊝⊝
low
25 per 100 26 per 100
(25 to 26)
Mediuma
50 per 100 51 per 100
50 to 53)
Higha
80 per 100 82 per 100
(80 to 84)
*The basis for the assumed risk (e.g. the median control group risk across studies) is provided in footnotes. The corresponding risk (and its 95% confidence interval) is based on the assumed risk in the comparison group and the relative effect of the intervention (and its 95% CI).
CI: confidence interval; RR: risk ratio.
GRADE Working Group grades of evidenceHigh certainty: we are very confident that the true effect lies close to that of the estimate of the effect.
Moderate certainty: we are moderately confident in the effect estimate; the true effect is likely to be close to the estimate of the effect, but there is a possibility that it is substantially different.
Low certainty: our confidence in the effect estimate is limited; the true effect may be substantially different from the estimate of the effect.
Very low certainty: we have very little confidence in the effect estimate; the true effect is likely to be substantially different from the estimate of effect.
a We selected low, medium and high illustrative retention levels of 25%, 50% and 80% based on prior experience with trial retention and evidence from the literature. For example, it has been previously stated that it is common for up to 20% trial participants to drop out before the trial finishes (Walsh 2015), as such we set the upper limit of good retention as 80%. The other extreme of 25% was informed by evidence that some trials (largely internet based) can have retention as low as 10% to 25% (Murray 2009). The mid point of 50% was a judgement made by the review team and was deemed appropriate given the evidence for the other parameters.