Evidence Summary

What is it?

A community-based intervention strategy is used where public volunteers are trained and used as research partners. This results in a peer-led follow-up strategy (e.g., through peer reminder calls).

Does it work?

A peer‐led follow‐up strategy may result in a large increase in retention.

How big is the effect?

An increase of 22% (95% confidence interval = 14% to 30%).

How certain are we?

GRADE Low certainty.


We recommend that trialists consider using a peer-led follow-up strategy.

How can I use this straight away?

See Resource bundle below for details on how to implement a peer-led follow-up strategy.

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 using a peer-led follow-up strategy. The chart below shows the impact of an absolute increase of 22% (95% CI = 14% to 30%). Retention is now 87%, which means our best estimate is that you would now have enough participants to meet the statistical power calculations.

Cumulative Meta-Analysis*

*Random effects model done using Comprehensive Meta-Analysis v4 (www.meta-analysis.com).
Differences >0% favour the intervention. The GRADE assessment is low because of the imprecision of a single study.

Resource Bundle


How to Cite

Citation: Ostrovska B. Evidence pack– Retention: Peer-led follow-up strategy (RET15), 2023, https://www.trialforge.org/retention-sector/peer-led-follow-up-strategy-id-ret15/.

More Information

  1. This summary is from the Cochrane review of strategies to improve retention in randomised trials (https://www.cochranelibrary.com/cdsr/doi/10.1002/14651858.MR000032.pub3/full).
  2. 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 large effect size 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 info@trialforge.org.
Version: v1.0 - 06/07/2023

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