Close this search box.

Emphasising pain in participant information (ID REC15)

Evidence Summary

What is it?

Participants are presented with a version of the study protocol that explicitly describes all procedures that may be painful or uncomfortable.

Does it work?

Emphasising pain in information may reduce recruitment.

How big is the effect?

A decrease of -29% (95% confidence interval = -48% to -10%).

How certain are we?

GRADE Low certainty.


We recommend that trialists only emphasise pain in participant information in the context of an intervention evaluation.

How can I use this straight away?

See Resource bundle below for details on how to use emphasise pain in participant information.

Practical Impact

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 emphasising pain in participant information. The chart below shows the impact of an absolute increase of -29% (95% CI = -48% to -10%). Recruitment is now 1%, which means our best estimate is that 3000 people would now need to be approached to recruit 30 of them.

Cumulative Meta-Analysis*

*Random effects model done using Comprehensive Meta-Analysis v4 ( 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– Recruitment: Emphasising pain in participant information (REC15), 2023,

More Information

  1. This summary is from the Cochrane review of strategies to improve recruitment in randomised trials (
  2. It was prepared with financial support from Evidence Synthesis Ireland.
  3. The ‘Does it work?’ statement is structured according to effect size and GRADE certainty as per GRADE Guidelines 26 ( The statement is for a large effect size and GRADE Low certainty.
  4. 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.
  5. If you have any questions contact
v2.0 - 10/07/2023
Scroll to Top