Strategies to improve recruitment to randomised controlled trials (Review)

Data collection and analysis We extracted data on: the method evaluated; country in which the study was carried out; nature of the population; nature of the study setting; nature of the study to be recruited into; randomisation or quasi-randomisation method; and numbers and proportions in each intervention group. We used a risk or odds ratio and their 95% confidence interval (CI) to describe the effect in individual trials. We assessed heterogeneity between trial results. Main results We identified 45 eligible trials (18 new to this update) withmore than 41,239 participants. There were 40 studies involving interventions aimed directly at trial participants, while five evaluated interventions aimed at people recruiting participants. All studies were in health care. Some interventions were effective in increasing recruitment: telephone reminders to non-respondents (odds ratio (OR) 1.95, 95% CI 1.04 to 3.66; two trials, 1058 participants), use of opt-out, rather than opt-in, procedures for contacting potential trial participants (RR 1.39, 95% CI 1.06 to 1.84; one study, 152 participants) and open designs where participants know which treatment they are receiving in the trial (RR 1.22, 95% CI 1.09 to 1.36; two studies, 4833 participants). However, some of these strategies have disadvantages, which may limit their widespread use. For example, opt-out procedures are controversial and open designs are by definition unblinded. The effects of many other recruitment strategies are unclear; examples include the use of video to provide trial information to potential participants and modifying the training of recruiters. Many studies looked at recruitment to hypothetical trials and it is unclear how applicable these results are to real trials. Authors’ conclusions There are promising strategies for increasing recruitment to trials: telephone reminders; requiring potential participants to opt-out of being contacted by the trial team regarding taking part in a trial, rather than them having to opt-in, and open designs. Some strategies (e.g. open trial designs) need to be considered carefully before use because they also have disadvantages. For example, opt-out procedures are controversial and open designs are by definition unblinded. P L A I N L A N G U A G E S U M M A R Y Strategies to recruit participants to randomised trials Many trials do not recruit sufficient participants and this can make it more difficult to use the results of the research in practice. Effective strategies for improving recruitment would be of great benefit to researchers designing and running trials. This review did find some strategies that can increase recruitment to trials. Researchers could telephone non-respondents to remind them about the trial. The research team could use opt-out, rather than opt-in, procedures for contacting potential trial participants, or they could use an open design where participants know which treatment they are receiving in the trial, rather than having some of them receive a placebo or dummy intervention to mask this. However, some of these effective strategies have disadvantages, which may limit their widespread use. The effect of many other recruitment strategies is unclear. Many studies have looked at recruitment to mock trials and it is difficult to know how their findings would apply to real trials. It would be better if more researchers included an evaluation of recruitment strategies in real trials. 2 Strategies to improve recruitment to randomised controlled trials (Review) Copyright © 2011 The Cochrane Collaboration. Published by John Wiley & Sons, Ltd. S U M M A R Y O F F I N D I N G S F O R T H E M A I N C O M P A R I S O N [Explanation] Telephone reminder versus no telephone reminder Patient or population: Individuals eligible for a trial Settings: Any Intervention: Telephone reminder Comparison: No telephone reminder Outcomes Illustrative comparative risks* (95% CI) Relative effect (95% CI) No of participants (studies) Quality of the evidence (GRADE) Comments Assumed risk Corresponding risk No telephone reminder Telephone reminder Number recruited Low1 OR 1.95 (1.04 to 3.66) 778 (2 studies) ⊕⊕⊕© moderate2 30 per 100 46 per 100 (31 to 61)