A questionnaire that covers issues relevant to the trial (e.g., a home safety questionnaire for an injury prevention trial) is added to the trial invitation pack.
Enclosing a questionnaire covering issues relevant to trial with the invitation probably increases recruitment.
An increase of 18% (95% confidence interval = 16% to 20%).
GRADE Moderate certainty.
We recommend that trialists consider enclosing a questionnaire covering issues relevant to the trial with the trial invitation.
See Resource bundle below for details on how to prepare a questionnaire covering issues relevant to the trial.
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 adding a questionnaire covering issues relevant to the trial to the invitation pack. The chart below shows the impact of an absolute increase of 18% (95% CI = 16% to 20%). Recruitment is now 48%, which means our best estimate is that 63 people would now need to be approached to recruit 30 of them.