Retention strategies for clinical trials; exploring the costs, planning and communication processes
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Full text E-thesis
Date
2025
Authors
Murphy, Ellen
Journal Title
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Volume Title
Publisher
University College Cork
Published Version
Abstract
Background
Participant retention in randomised controlled trials is an ongoing challenge for trial teams. If trials lose large numbers of participants, the trials’ ability to answer the research question is jeopardised. Trial teams often use retention strategies, activities aimed at facilitating ongoing trial participation, to reduce missing data and improve data completeness. There are several gaps in the literature on the costing, planning, and communication of retention strategies. Thus, the aim of this doctoral thesis is to investigate the costing, planning, and communication of retention strategies, specifically focusing on the trial design, planning, and consent stages.
Methods
This is a multi-phase sequentially mixed-methods thesis, which contains discrete (mixed) chapters, concluding with the overall findings synthesised. A pragmatic, mixed-methods research approach was taken. Chapter Four applies a costing approach to generate estimated costs of implementing retention strategies in trials. Chapter Five presents a scoping review investigating whether trial teams are planning retention strategies during the trial design stage. A content analysis of participant information leaflets (PILs) is presented in Chapter Six, to establish if potential trial participants are being informed about retention strategies during informed consent. Chapter Seven reports one-to-one interviews with trialists to get a more in-depth understanding of the planning and communication of retention strategies. Chapter Eight discusses the integrated findings in the context of the wider literature.
Findings
The planning and implementation of retention strategies in practice are better than their reporting in trial documents. Trialists typically plan retention strategies during the trial design and planning stages. However, if participant retention rates become a concern, retention strategies are also planned and implemented in real-time as the trial progresses. A wide range of both formal and informal strategies are used by trial teams to promote continued participation in trials. Formal strategies include: prompts, reminders, newsletters, monetary incentives, and offering different options for data collection according to participant preference. Informal strategies include building rapport with participants and having motivated trial staff. Unfortunately, the reporting of retention strategies in trial protocols is frequently inadequate, with protocols rarely outlining these methods despite best practice recommendations to do so. Trialists cite various reasons for this poor reporting. Even though the planning and implementation of retention strategies is common, research is needed to improve evidence-based decision making for trialists. Currently, trial teams often rely on personal experience when choosing strategies due to a lack of high-quality evidence demonstrating that retention strategies are effective at improving retention rates. Formal evaluations of strategy effectiveness are needed to reduce this evidence gap. Furthermore, retention strategies can be extremely costly and resource intensive, which underscores the need for evidence to determine which retention strategies justify the investment. Documentation practices around retention strategies, and the importance of retention, in PILs is variable. More research is necessary to understand participants’ perspectives on how, and when, they would prefer to receive communications about retention strategies and the importance of staying involved in trials.
Conclusion
Planning and implementing retention strategies is common, while the reporting of these strategies in trial documents tends to be inconsistent. There is a need to enhance the reporting of retention strategies in trial protocols, and to better understand the most effective ways to communicate retention strategies, and the importance of trial participation, to participants. Trial teams must consider numerous factors when planning and communicating retention strategies. However, more research is needed to support evidence-based decision-making in this area.
Description
Keywords
Retention , Retention strategies , Activities to promote participant retention , Trials , Clinical trials , Randomised controlled trials , Costing , Planning , Communication , Implementation , Trial methodology research , Trial design , Protocol development , Informed consent
Citation
Murphy, E. 2025. Retention strategies for clinical trials; exploring the costs, planning and communication processes. PhD Thesis, University College Cork.