Enclosing a questionnaire covering issues relevant to trial with the invitation
Enclosing a questionnaire covering issues relevant to trial with the invitation probably increases recruitment.
The absolute increase is 5% (95% CI = 2% to 8%)1
MODERATE CERTAINTY in the evidence (but see 'What we don't know' below)
1 Treweek S, Pitkethly M, Cook J, Fraser C, Mitchell E, Sullivan F, Jackson C, Taskila TK, Gardner H. Strategies to improve recruitment to randomised trials. Cochrane Database of Systematic Reviews 2018, Issue 2.
The practical impact of enclosing a questionnaire covering issues relevant to trial with invitation
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 (see chart below).
Now imagine enclosing a questionnaire with the invitation. The chart below shows the impact of an absolute increase of 5% (95% CI =2% to 8%)1. Recruitment is now 35%, which means our best estimate is that 86 people would need to be approached to recruit 30 of them.
Where has enclosing a questionnaire covering issues relevant to trial with the invitation been tested?
Study 1: Kendrick 2001
Families with children aged under 5 years, living in deprived areas.
Health visitor advice and low cost safety equipment.
Primary care, UK.
18% of participants randomised to receive a questionnaire were recruited; 13% of participants randomised to not get a questionnaire were recruited
What we still don’t know about enclosing a questionnaire covering issues relevant to trial with the invitation
- The GRADE assessment is still only moderate for this intervention because there is only a single evaluation. More evaluations in any type of trial are needed.
- Please get in touch (email firstname.lastname@example.org) if you would like to do an evaluation because we can help with text for ethics etc.