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PIL development #1: a bespoke, user-centred process (ID REC5)

Evidence Summary

What is it?

Bespoke Participant Information Leaflet (PIL).

Does it work?

Optimising the participant information leaflet (PIL) through a particular, bespoke process involving formal user testing makes little or no difference to recruitment.

How big is the effect?

An increase of 1% (95% confidence interval = -1% to 3%).

How certain are we?

GRADE High certainty.


We recommend against using this intervention with the intention of increasing recruitment. Evaluation outside the UK would be useful.

How can I use this straight away?

See Resource bundle below for details of how to use bespoke Participant Information Leaflets (PIL) or build a SWAT evaluation of them into your trial.

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 using a bespoke user-centred PIL development process. The chart below shows the impact of an absolute increase of 1% (95% CI = 1-% to 3%). Recruitment is now 31%, which means our best estimate is that 97 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 moderate because of imprecision.

Resource Bundle

How to Cite

Citation: Treweek S, Bruhn H, Gardner H. Evidence pack­– Recruitment: Email invitations (Rec9), 2021,

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 trivial, small unimportant or no effect size and GRADE moderate 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
v1.0 - 17/12/2021
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