Methodological guidance for incorporating lived experience in the early stages of core outcome set development: a scoping review

BACKGROUND: Core Outcome Sets (COS) provide a systematic approach to ensuring that outcomes measured in health research matter to the individuals most affected by the research. While methodological guidance generally exists for COS development, specific guidance on incorporating the perspectives of people with lived experience (PWLE) during the long-list stage remains fragmented and unclear. This stage is crucial for including outcomes that matter to those directly impacted. Therefore, this scoping review aims to systematically identify and chart the available methodological literature on incorporating the perspectives of PWLE into the long-list generation stage of COS development. METHODS: This review followed JBI guidance for scoping reviews and adhered to PRISMA-ScR reporting standards. A comprehensive search was conducted across multiple databases (MEDLINE, Embase, Scopus, CINAHL, ProQuest Theses & Dissertations, and the COMET Database) on 31 October 2024. In addition, a citation search of all included articles and further expert consultation were included to ensure that all relevant articles were identified. Articles were eligible for inclusion if they provided methodological guidance, recommendations and/or insight into how best to include the perspectives of PWLE into the long-list stage of COS development. Screening and data extraction were completed by two independent reviewers. The analysis was guided by a combined deductive-inductive qualitative content analysis process. Categories were developed from the data and synthesised into practical recommendations for COS developers. RESULTS: A total of 45 articles were included. The analysis yielded four major categories of guidance: (1) PWLE Identification, Recruitment, and Engagement; (2) Data Collection Considerations; (3) Analysis and Reporting; and (4) Contextual Considerations. The results highlight an evolving methodological landscape surrounding PWLE perspective integration into COS development. The results emphasise the importance of purposeful and reflexive methodological choices and underscore the importance of utilising existing qualitative research, participatory action research (PAR), reporting standards, and existing equity, diversity, and inclusion principles throughout the long-list process. CONCLUSIONS: This review identified a growing but uncoordinated body of methodological guidance for including the perspectives of PWLE into the long-list stage of COS development. The findings will support future COS developers in making methodologically rigorous decisions. Future research should aim to validate these findings and recommendations through empirical work with COS developers and PWLE, informing the co-production of best practice guidelines. TRIAL REGISTRATION: This review is registered in the COMET Database: https://www.comet-initiative.org/Studies/Details/3590. The protocol for this review is available at https://doi.org/10.1186/s13063-025-09149-2.