The cost-effectiveness of Studies Within A Trial (SWATs) for improving recruitment and retention in randomised trials

Background: Randomised controlled trials (RCTs) constitute the gold-standard design for evaluating interventions. However, their design, conduct and validity can be threatened by slow recruitment of invited patients and/or attrition of already recruited participants. Given such challenges, the research community is increasingly interested in identifying effective recruitment and retention strategies via the conduct of Studies Within A Trial (SWATs). Aims: This thesis applies economic techniques to demonstrate the significance of trial recruitment and retention, and to introduce economic methods for improving the evaluation of recruitment and retention strategies via SWATs.
Methods: The thesis employs a wide range of health economic methods, including decision modelling, costing analysis, systematic review and Value of Information (VoI) analysis. Results: Chapter 2 presents the impact of slow recruitment to the RECOVERY trial generated opportunity costs due to the delayed dissemination of a more cost-effective, available treatment for hospitalised COVID-19 patients. Chapter 3 highlights that participant loss to follow-up from the Occupational Therapist Intervention Study (OTIS) trial generated significant financial costs to the trial team and funder, despite its low attrition rate. Chapter 4 critically appraises the evidence surrounding the cost-effectiveness of recruitment and retention strategies, concluding that no cost-effective strategy exists with high certainty of evidence, due to the limited availability of economic evaluations alongside most SWATs. Finally, considering the limited resources for funding future SWATs, Chapter 5 introduces and applies a Value of Information (VoI) analysis framework to telephone reminders (recruitment strategy) and pens (retention strategy), showing that such a methodology can be feasibly used as a tool, alongside Trial Forge Guidance 2, for prioritising research on recruitment and retention strategies. Conclusion: Integrating economic evaluations into SWATs and using VoI analyses can strengthen future SWAT-related research, allowing trial methodologists to improve the conduct of their studies.