Evidence Summary

What is it?

Participants are recruited and receive reminders via a telephone call which is conducted by members of the group you are trying to recruit.

Does it work?

An enhanced recruitment package including more contact by telephone may make little or no difference in recruitment.

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 use enhanced recruitment packages with more telephone contact in the context of an intervention evaluation.

How can I use this straight away?

See Resource bundle below for details on how to prepare enhanced recruitment packages with more telephone contact.

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 an enhanced recruitment package with more contact by telephone. The chart below shows the impact of an absolute increase of 0% (95% CI = -1% to 0%). Recruitment is still 30%, which means our best estimate is still that 100 people would now need to be approached to recruit 30 of them.

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: Treweek S, Bruhn H, Gardner H. Evidence pack­– Recruitment: Enhanced recruitment package with more telephone contact (REC13), 2023, https://www.trialforge.org/recruitment-sector/enhanced-recruitment-package-with-more-telephone-contact-id-rec13

More Information

  1. This summary is from the Cochrane review of strategies to improve recruitment in randomised trials (https://doi.org/10.1002/14651858.MR000013.pub6).
  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 (https://doi.org/10.1016/j.jclinepi.2019.10.014). The statement is for trivial, small unimportant effect or no effect 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 info@trialforge.org.
Version: v2.0 - 10/07/2023

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