Skip to main content

Research Repository

Advanced Search

Impact of patient and public involvement on enrolment and retention in clinical trials: Systematic review and meta-analysis

Crocker, Joanna C; Ricci-Cabello, Ignacio; Parker, Adwoa; Hirst, Jennifer A; Chant, Alan; Petit-Zeman, Sophie; Evans, David; Rees, Sian


Joanna C Crocker

Ignacio Ricci-Cabello

Adwoa Parker

Jennifer A Hirst

Alan Chant

Sophie Petit-Zeman

David Evans
Professor in Health Services Research

Sian Rees


© Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to. Objective To investigate the impact of patient and public involvement (PPI) on rates of enrolment and retention in clinical trials and explore how this varies with the context and nature of PPI. Design Systematic review and meta-analysis. Data sources Ten electronic databases, including Medline, INVOLVE Evidence Library, and clinical trial registries. Eligibility criteria Experimental and observational studies quantitatively evaluating the impact of a PPI intervention, compared with no intervention or non-PPI intervention(s), on participant enrolment and/or retention rates in a clinical trial or trials. PPI interventions could include additional non-PPI components inseparable from the PPI (for example, other stakeholder involvement). Data extraction and analysis Two independent reviewers extracted data on enrolment and retention rates, as well as on the context and characteristics of PPI intervention, and assessed risk of bias. Random effects meta-analyses were used to determine the average effect of PPI interventions on enrolment and retention in clinical trials: main analysis including randomised studies only, secondary analysis adding non-randomised studies, and several exploratory subgroup and sensitivity analyses. Results 26 studies were included in the review; 19 were eligible for enrolment meta-analysis and five for retention meta-analysis. Various PPI interventions were identified with different degrees of involvement, different numbers and types of people involved, and input at different stages of the trial process. On average, PPI interventions modestly but significantly increased the odds of participant enrolment in the main analysis (odds ratio 1.16, 95% confidence interval and prediction interval 1.01 to 1.34). Non-PPI components of interventions may have contributed to this effect. In exploratory subgroup analyses, the involvement of people with lived experience of the condition under study was significantly associated with improved enrolment (odds ratio 3.14 v 1.07; P=0.02). The findings for retention were inconclusive owing to the paucity of eligible studies (odds ratio 1.16, 95% confidence interval 0.33 to 4.14), for main analysis). Conclusions These findings add weight to the case for PPI in clinical trials by indicating that it is likely to improve enrolment of participants, especially if it includes people with lived experience of the health condition under study. Further research is needed to assess which types of PPI work best in particular contexts, the cost effectiveness of PPI, the impact of PPI at earlier stages of trial design, and the impact of PPI interventions specifically targeting retention. Systematic review registration PROSPERO CRD42016043808.


Crocker, J. C., Ricci-Cabello, I., Parker, A., Hirst, J. A., Chant, A., Petit-Zeman, S., …Rees, S. (2018). Impact of patient and public involvement on enrolment and retention in clinical trials: Systematic review and meta-analysis. BMJ, 363(8178), Article k4738.

Journal Article Type Article
Acceptance Date Oct 30, 2018
Online Publication Date Nov 28, 2018
Publication Date Dec 1, 2018
Deposit Date Jan 4, 2019
Publicly Available Date Jan 4, 2019
Journal BMJ (Online)
Print ISSN 1756-1833
Electronic ISSN 1756-1833
Publisher BMJ Publishing Group
Peer Reviewed Peer Reviewed
Volume 363
Issue 8178
Article Number k4738
Public URL
Publisher URL


You might also like

Downloadable Citations