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Post-it note (ID RET17)

Evidence Summary

What is it?

As follow-up participants receive a handwritten or printed post-it note either alone or with usual follow-up or a newsletter. The note contains text such as “Please take a few minutes to complete this for us. Thank you.”

Does it work?

Addition of a post‐it note may result in little or no difference to retention.

How big is the effect?

An increase of 0% (95% confidence interval = -1% to 1%).

How certain are we?

GRADE Low certainty.


We recommend that trialists add post-it notes to follow-up in the context of an intervention evaluation.

How can I use this straight away?

See Resource bundle below for support materials.

Practical Impact

Imagine initial retention is 65% of those approached. You have a trial with 100 participants that needs responses from 80 to meet its statistical power calculations.  Retention of 65% means that you will be 15 responses short (see chart below).

Now imagine adding post-it notes to follow-up. The chart below shows the impact of an absolute increase of 0% (95% CI = -1% to 1%). Retention remains unchanged.

Cumulative Meta-Analysis*

*Random effects model done using Comprehensive Meta-Analysis v4 ( Differences >0% favour the intervention. The GRADE assessment is low because of imprecision.

Resource Bundle

How to Cite

Citation: Ostrovska B. Evidence pack– Retention: Post-it note (RET17), 2023,

More Information

  1. This summary is from the Cochrane review of strategies to improve retention in randomised trials (
  2. The ‘Does it work?’ statement is structured according to effect size and GRADE certainty as per GRADE Guidelines 26 ( The statement is for trivial, small unimportant effect or no effect and Low GRADE certainty.
  3. 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.
  4. If you have any questions contact
v1.0 - 06/07/2023
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