A Qualitative Exploration of Patient and Public Involvement Experiences in Core Outcome Set Development: Insights From Public Partners and Research Stakeholders

INTRODUCTION: Patient and public involvement (PPI) in research engages patients and the public in all aspects of the research process, ensuring that the perspectives of those directly affected by healthcare systems are integral to decision-making processes. PPI is recognised as central to the development of Core Outcome Sets (COS), standardised collections of outcomes that should be reported in all clinical trials. Despite agreement on the importance of PPI, limited evidence exists on the experience of PPI across partners and research stakeholders. This study explored experiences of PPI during the development of a Core Outcome Set (COS) for dental behaviour support (DBS), with recommendations for better practice. METHODS: Qualitative data were collected through semi-structured group discussions and individual interviews with PPI partners and key research stakeholders who designed, coordinated, or worked alongside the PPI process. Transcripts were analysed using iterative reflexive thematic analysis. Themes were developed and refined through continuous engagement with PPI partners, who provided feedback to shape interpretation and ensure authenticity. Data management and coding were conducted using NVivo (QSR International Pty Ltd, Version 12). RESULTS: Four themes captured partners' experiences of PPI within COS development. These highlighted the importance of managing expectations, creating a supportive and inclusive environment, and fostering opportunities for shared learning and reflection. Ten participants were interviewed, including PPI partners and key research stakeholders. Partners described how meaningful involvement changed their understanding of research and strengthened the partnership between researchers and the public. Practical recommendations were shared for future PPI engagement in COS studies. CONCLUSION: Effective PPI in COS development requires clear role definition, inclusive collaboration, and ongoing reflexivity. A dedicated PPI Coordinator plays a vital role in supporting communication, trust, and PPI partner empowerment, ensuring participants are valued as co-developers rather than passive reviewers. PATIENT AND PUBLIC CONTRIBUTION: PPI partners initiated this study, participated as interviewees, supported data interpretation, and co-authored this paper.