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

Abstract

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.

Supplementary Information

The online version contains supplementary material available at https://doi.org/10.1186/s13063-026-09848-4.

Background

Clinical research faces persistent challenges with outcome heterogeneity. Studies investigating the same condition, intervention, or phenomena rarely measure the same outcomes or measure common outcomes in the same way. This impedes the conduct of systematic reviews with meta-analyses, contributes to the proliferation of research waste [1], and can lead to the omission of outcome measures that are important to interest-holders who benefit the most from clinical research [2]. The lack of standardisation of outcomes across clinical research also restricts evidence synthesis, making it challenging for providers and policymakers to evaluate and compare the effectiveness of interventions and leads to a disconnect between the evaluation of new interventions and their integration into evidence-based healthcare decision making [3].

The role of Core Outcome Sets

One effective way to address the challenge of outcome heterogeneity and associated research waste implications in clinical research is the development and implementation of Core Outcome Sets (COS). COS are an agreed-upon, standardised set of outcomes that should be measured and reported in all clinical trials within a specific health domain [4]. The development of COS can be traced back to the Outcome Measures in Rheumatology (OMERACT) Initiative, which pioneered structured consensus processes to standardise outcome reporting in rheumatology research [5]. Building on this foundation, the Core Outcome Measures in Effectiveness Trials (COMET) Initiative has expanded the concept of COS, providing methodological guidance for developing COS and maintaining a database of ongoing and completed COS studies [4]. By ensuring consistency in outcome reporting, COS aim to enhance the comparability, relevance, and impact of clinical trials, facilitating more effective evidence synthesis and improving research translation into evidence-based practice [3].

As a means of providing support to COS developers, the COMET Initiative has published a roadmap for COS development, the COMET Handbook V1.0 [6]. This handbook outlines a multistage COS development process beginning with the establishment that a COS in a specific health domain is needed. The handbook advises next to compile a comprehensive “long-list” of all potential outcomes to be measured in the specified health domains. In subsequent stages, they recommend refining this long-list through a consensus process involving various interest-holders, ultimately resulting in a final must-have list of outcomes to include in a COS. COMET emphasises that COS should include outcomes that are important to all interest-holders, including but not limited to PWLE of a condition and/or intervention, caregivers, other service users, and healthcare professionals, and they recommend that these interest-holders be included in the COS development process [6, 7]. Studies indicate that when patients or their representatives are actively involved in COS development, the impact of interventions on patients’ lives is more likely to be represented in the COS [8]. Moreover, COS developers have noted that the perspective of interest-holders during the long-list stage has contributed unique outcomes, which were ultimately included in the final COS [8].

Although the handbook [6] offers a comprehensive outline for COS development, it noted at the time of publication in 2017 that the field was still in its infancy and calls for further methodological research. Since then, COS development has proliferated, with approximately 50 new COS published annually, thus generating a potentially significant number of COS-related methodological explorations that may warrant updated guidance [7]. Publications dated prior to and after the COMET Handbook reinforce the need for additional guidance on methodological decisions surrounding best practices for interest-holder inclusion into COS development [9–11].

Current methodological gaps

Within the COS development process, the timing of the inclusion of the lived-experience perspectives is not specified by the COMET handbook [6]. The timing of this participation carries significant methodological and ethical implications. If PWLE are limited to participation in the consensus stages, the problem of only measuring what is important to researchers is not solved but rather reinforced. Tokenistic participation from PWLE is also risked by limiting their involvement to later stages; this generally serves as a validation of the long-list rather than an equitable, multi-interest-holder engagement process of building the long-list [12]. Early engagement, in the long-list stage of development, provides an excellent way of ensuring that outcomes brought to the consensus process include what is important to all lived experience contributors.

Given the current methodological gap when seeking to include the perspectives of PWLE in this early and critical long-list stage of COS development, there is a need for a systematic identification and charting of existing approaches. The findings of this review have the potential to affect future COS development projects via enhanced methodological rigour on PWLE inclusion practices. As a result, this review helps to inform best practices and ensure that COS development aligns more closely with the priorities of those most affected by health care research.

Key terms and definitions

The COMET Handbook distinguishes between two forms of patient and public engagement in COS development: research participation, where individuals contribute their views on the importance of outcomes as research participants, and patient and public involvement (PPI), where individuals act as research partners in the design and oversight of the study [6]. This review focuses on the former, the inclusion of individuals with direct experience of the illness, treatment, or care process relevant to the COS, who engage as participants contributing their perspectives on outcomes rather than as research partners or advisors [6]. Throughout this review, the term “participation” is used to refer to this direct inclusion of lived experience contributors in the research process, while “involvement” is reserved for the engagement of individuals in a PPI advisory or oversight capacity. The term “people with lived experience” is used to refer to individuals whose inclusion is sought on the basis of their direct experiential knowledge of the condition and/or intervention under study, consistent with the characterisation of “participants” in the COMET Handbook [6].

Objectives

The objective of this scoping review was to systematically identify and chart the available methodological literature on how to incorporate the perspectives of those with lived experience into the long-list generation stage of COS development.

Public and patient involvement

Public and patient involvement (PPI) was integrated throughout this scoping review through partnership with an individual with direct clinical trial participation experience and leadership roles in patient advocacy organisations for an inherited genetic condition. Partnership activities included the following: (1) protocol development, including objective refinement, methodological validation, and final approval; (2) review execution, including regular updates on the screening, review and feedback on preliminary and final results and review and feedback on the writing of the final manuscript; and (3) knowledge translation and co-development of plain-language outputs. The PPI contributor helped shape decisions surrounding the presentation of the results and resulting recommendations, specifically by validating the recommendations and assisting with descriptions provided in the discussion. The public partner maintained an advisory role, declining offered co-authorship opportunities.

Methods

This scoping review was conducted following the Joanna Briggs Institute (JBI) guidance for scoping reviews [13] and reported according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses Extension for Scoping Reviews (PRISMA-ScR) [14] and the Guidance for Reporting Involvement of Patients and Public, Short Form (GRIPP2-SF) [15]; completed checklists are available in the supplementary materials. A scoping review methodology was chosen because it allowed for systematic identification and charting of the evidence on incorporating the perspectives of those with lived experience into the long-list generation stage of COS development without assessing the quality or strength of the evidence. The protocol for this review was developed a priori [16]. Any deviations from the protocol are reported within the “Methods” section.

Data sources and search strategy

A comprehensive search was conducted on 31 October 2024 across six databases: Embase, Scopus, MEDLINE via EBSCO, CINAHL via EBSCO, ProQuest Theses and Dissertations, and the COMET Database. Prior to the final search, an initial piloting search strategy was developed collaboratively with a health research librarian and conducted in MEDLINE via EBSCO. Further refinements were made, and a final search strategy was developed and run in MEDLINE via EBSCO. The search strategies were built on three core concepts: “individuals and/or groups”, “core outcome sets”, and “lived experience”. A combination of search keywords, subject headings, and MeSH terms were used to develop searches. The final piloted and validated MEDLINE via EBSCO strategy was then translated into CINAHL via EBSCO, Embase, and Scopus. A separate strategy was developed for ProQuest, and the COMET Database was included in its entirety.

All final search strategies were peer reviewed by a health research librarian via the Peer Review of Electronic Search Strategies (PRESS) Checklist [17] to ensure that all relevant records were obtained to meet the aims of this review. Complete search strategies for all included databases are available in the supplementary materials.

Eligibility criteria

Inclusion criteria

Records were included if they were peer-reviewed literature and/or grey literature, such as theses, dissertations, primary studies, secondary syntheses, and/or conference proceedings. The included articles needed to report recommendations, guidance, and/or insights into what should be done to include the perspectives of PWLE in the long-list stage of COS development in the field of health research. There were no restrictions on the length of the text in the articles presenting recommendations; even brief guidance provided in a few sentences qualified for inclusion. No date restrictions were imposed.

Exclusion criteria

Articles were excluded if they were protocols, did not provide methodological guidance, were published in languages other than English, or described methodological guidance in COS designated for non-health-related areas.

In addition, articles whose primary purpose was to report a final COS for practice and/or research were excluded. Although some of these publications may have included brief methodological reflections or commentary, the aim of this review was to identify literature with an explicit focus on methodological guidance, insights, recommendations, or learning arising from COS development processes. Accordingly, final COS publications were considered outside the scope of this review.

Screening and study selection process

Article management process

All articles retrieved from database searching underwent citation management via EndNote and Covidence. Duplicates were removed using built-in capabilities in EndNote and Covidence in addition to hand-removal where necessary. After screening, the included articles were catalogued into an Excel file.

Article screening process

Title and abstract screening were conducted independently in Covidence by two reviewers (MKL and KR). All articles included after title and abstract screening were then subjected to full-text screening by two independent reviewers (MKL and KR). All articles that were included after full-text screening underwent a manual search of their reference lists. Reference-list checking was completed by one reviewer (MKL). Any articles from reference checking that progressed to full-text screening were uploaded to Covidence for full evaluation by two independent reviewers (MKL and KR). Any disagreements between the reviewers during any stage of screening were resolved through discussion. If consensus was not reached, a third reviewer (ET) was consulted to make the final decision on inclusion.

The final included article list, PRISMA-ScR flow diagram, and a copy of the review protocol were sent to the COMET Initiative via their generic contact email address. At this stage, COMET were asked to review the information provided and note any potentially missing articles from the final inclusion list. No additional included articles were identified via consultation with COMET.

Data extraction process

A data extraction tool was developed iteratively during the early stages of screening to capture information relevant to the research aim in a structured format that facilitated comparisons and connections between the included articles. The finalised tool (available in Additional file 4.pdf – Sample data extraction form) included the following elements: (1) study identifier/DOI/COMET ID and Covidence identifier, (2) title of the study, (3) publication month/year, (4) publication source and type, (5) lead author, (6) aim and/or purpose of the study (one to two sentence summary), (7) methodological guidance provided, (8) identified challenges/barriers and/or facilitators to the involvement of PWLE and (9) reported gaps in methodological guidance. Wherever possible, the extracted data were verbatim text from the articles, with corresponding pages/line locations.

Articles identified for inclusion after full-text screening were subjected to data extraction. An initial 10% of the articles were extracted and compared by the two reviewers (MKL & KR) to refine and finalise the data extraction form. Data extraction was independently completed by two reviewers for 100% of the remaining included articles. Throughout data extraction, both reviewers met regularly to discuss their findings and to ensure that all relevant material was extracted from each article. When disagreements occurred, a third reviewer (ET) was consulted. As a final step, the data extracted from each reviewer were merged into one final form. Data from this final form were included in the analysis process.

Data analysis and presentation

Data analysis and presentation were conducted in accordance with JBI guidance for scoping reviews, which supports the use of basic qualitative content analysis as an appropriate approach to charting and describing heterogenous, textual evidence sources [13]. To help structure this descriptive charting process, Mayring’s [18] qualitative content analysis framework was used, specifically by utilising a coding process that combines inductive and deductive category development. This approach was selected because it allows for a transparent and systematic scaffold for the extraction and basic charting of data from diverse literature sources.

Initially, during the screening and data extraction process, four major categories were developed inductively based on the research objectives and patterns identified from reading the data. These initial categories were developed collaboratively by both data extractors through a comprehensive review of the entire dataset and discussions framed around the research objectives. All extracted data were then uploaded to QUIRKOS qualitative data analysis software [19] and deductively coded into these four major category areas via line-by-line coding; data were permitted to be coded into multiple categories where appropriate. Subcategories were developed inductively from the data coded into each major category area. This involved creating detailed descriptive codes that captured specific points of methodological guidance. All data with associated subcategories were subsequently uploaded to Excel, where the four major category areas, subcategories, and individual codes were further refined via discussion between two reviewers (MKL & KR). As a final step, the identified major categories, sub-categories, and codes informed the development of practical recommendations for COS developers. These recommendations, presented in the “Discussion”, represent an interpretive synthesis of the findings rather than a direct output of the descriptive analysis.

The results are presented narratively and organised by reporting the article characteristics followed by the four major category areas, with corresponding subcategories, accompanied by tables describing each. This analysis approach allowed for systematic charting of available methodological guidance while maintaining sensitivity to the diversity of insights, guidance, and recommendations present in the literature.

Results

Description of the included articles

A total of 45 articles were included in this review. Forty-four articles were identified via database searches (see Fig. 1: PRISMA flow diagram [14]), and one was identified via citation searching. Articles were published across 26 different publication sources. A small number of publication sources were overrepresented in the list, including the Journal of Clinical Epidemiology (n = 8) [20–27], BMC Trials (n = 5) [6, 28–31], Research Engagement and Involvement (n = 5) [32–36], and PLOS One (n = 4) [37–40]. Two of the four included theses were authored by researchers from the University of Liverpool [9, 41]. All other publication sources contributed singular articles (n = 21) [10, 11, 42–60].

Fig. 1.

PRISMA flow diagram [14]

The earliest included article was published in 2012 [28]. All but 12 of the included articles [6, 9, 25, 28–30, 32, 39, 40, 42, 46, 60] were dated between 2018 and 2025, with 2017 being the year the COMET Handbook V1.0 [6] was published. Most of the included articles were classified as research articles (n = 13) [11, 25, 31, 36, 37, 43, 44, 48, 54–56, 58, 59] or review articles (n = 7) [26, 38–40, 47, 49, 53]. Six included articles were from a series titled “Controversy and Debate Series on Core Outcome Sets” (n = 6) [20–24, 27], and another six were commentaries (n = 6) [28, 32–34, 50, 57]. Four theses were also included [9, 10, 41, 42]. Six distinct aim categories were identified: (1) Methodological Development and Exploration (n = 19) [6, 9, 10, 25, 28–32, 35, 39–42, 46, 56, 58–60]; (2) Interest-Holder Involvement and Engagement Practices (n = 29) [10, 11, 25, 26, 28–38, 40–44, 47, 49–51, 54–58]; (3) COS Landscape Mapping and Systematic Assessment (n = 11) [9, 25, 26, 31, 33, 38–40, 48, 49, 53]; (4) Implementation, Uptake, and Knowledge Translation (n = 6) [6, 9, 11, 34, 39, 60]; (5) Condition-Specific COS Development (n = 9) [11, 36, 45, 50, 51, 54–56, 58]; and (6) Methodological Innovation and Controversy (n = 6) [20–24, 27]. Each article was assigned to one or more aim category based on their stated aim. A complete list of included articles with publication types, sources, and assigned aim categories is provided in the supplementary materials. Descriptions of each aim category are provided in Table 1.

Table 1.

Included article aim categories and definitions

Aim category	Definition
Methodological development and exploration	Investigation of COS development methodology and approaches; exploration of consensus methods and their impact on outcome identification; development of methodological frameworks and standards; comparison of different methodological approaches
Interest-holder involvement and engagement practices	Patient and public involvement in COS development; interest-holder engagement methods and experiences; inclusive participation across diverse populations; methods for involving specific populations, e.g. children, low- and middle-income countries (LMICs) interest-holders
COS landscape mapping and systematic assessment	Systematic reviews of existing COS; mapping of COS availability across clinical areas; assessment of COS development patterns and trends
Implementation, uptake, and knowledge translation	COS implementation and adoption in research; knowledge translation frameworks; barriers and facilitators to COS use
Condition-specific COS development	Development of COS for specific clinical conditions; application of COS methodology to particular health areas
Methodological innovation and controversy	Debates about COS development approaches; proposals for methodological improvements and alternatives

Key findings

A total of four major category areas were identified during analysis of the extracted data: (1) PWLE Identification, Recruitment, and Engagement, (2) Data Collection Considerations, (3) Analysis and Reporting, and (4) Contextual Considerations. They are presented below with corresponding subcategories and codes, with descriptions of the identified and synthesised guidance and accompanying tables for each subcategory.

PWLE identification, recruitment, and engagement

All but six articles [22, 29, 48, 52, 56, 58] provided guidance on identifying, recruiting, retaining, or integrating meaningful engagement of lived experience contributors.

Defining and identifying lived experience contributors

Twenty-four articles [6, 9, 25, 26, 28, 30–32, 35–41, 43, 46, 47, 49, 50, 53, 54, 57, 59, 60] included specific guidance related to predetermining “who” should be involved as a PWLE during the planning and design phase of COS development (Table 2). Guidance encouraged developers to be purposeful in planning to include patients before recruitment begins, recommending that, when seeking lived experience contributors “… participants should exclusively be people who have personal experience of the condition or situation ([41], p. 40)”. Some authors have suggested that it may be sufficient to include persons representing condition-specific representative organisations or healthcare providers working in these healthcare areas rather than those with direct lived experiences; however, methodological guidance consistently emphasises that clearly described reasoning is needed and justification for “who” is chosen to be involved and “why” must be established and documented at the protocol development stage [46, 47].

Table 2.

Defining and identifying lived experience contributors

Sub-category	Code	Description	Contributing articles
Defining and identifying lived experience contributors (n = 24)	Recommendations for experience-based selection criteria (n = 21)	Recommends selecting PWLE based on relevant experiential knowledge (e.g. condition, treatment journey, caregiving)	[6, 9, 25, 26, 28, 30–32, 35, 37–41, 43, 46, 49, 53, 57, 59, 60]
	Guidance on defining PWLE roles and types (n = 11)	Recommends clarifying roles (e.g. patient advocate, caregiver, survivor) and differentiates types of lived experience contributors	[9, 25, 26, 28, 35, 43, 46, 53, 54, 57, 60]
	Recommendations for accessing PWLE populations (n = 9)	Recommends accessing PWLE via clinics, advocacy networks, community organisations, etc	[6, 9, 26, 28, 32, 43, 54, 57, 60]
	Guidance for equitable PWLE identification (n = 18)	Recommends strategically planning and documenting who should be represented prior to recruitment commencing, with the aim of avoiding selection bias and ensuring diversity goals are established at the protocol stage	[6, 9, 25, 28, 30, 32, 36–39, 46, 47, 49, 50, 53, 54, 59, 60]

Recruitment strategies and sampling logic

Thirty-four articles provide methodological recommendations surrounding the sampling and recruitment of PWLE [6, 9–11, 20, 21, 24, 25, 27, 28, 30–32, 34–47, 49, 51, 53–55, 60] (Table 3). This section focuses on recommendations for the sampling of participants for primary data collection activities at the long-list stage, such as qualitative interviews, focus groups, and surveys, rather than the recruitment or selection of PPI or PPIE partners in an advisory capacity. Twelve articles [11, 21, 25, 28, 30, 32, 34, 41, 43, 46, 60] advised having a clear plan in advance, being pragmatic about sampling decisions, and tailoring recruitment to the COS aim, such as sample size and diversity being dependent on the aim of the COS [30]. When surveys involving PWLE are used, achieving adequate sample diversity and comprehensiveness was highlighted as being “critical when the objective is to avoid overlooking outcome domains” ([27], p. 210). It was recommended that decisions around sampling and recruitment “should be documented and explained” in advance and in the final reporting of the COS ([28], p. 3).

Table 3.

Recruitment strategies and sampling logic

Sub-category	Code	Description	Contributing articles
Recruitment strategies and sampling logic (n = 34)	Sampling approaches and rationale (n = 23)	Recommends having a clear plan in advance and being pragmatic about sampling decisions; recommends tailoring recruitment to the COS aim as sample size and diversity being dependent on the aim of the COS	[9–11, 24, 25, 27, 30–32, 37–44, 46, 47, 49, 53, 55, 60]
	COS-specific recruitment rationale (n = 12)	Recommends aligning recruitment rationale with the intended scope and context of the COS being developed	[11, 21, 25, 27, 28, 30, 32, 34, 41, 43, 46, 60]
	Inclusive and flexible recruitment techniques (n = 25)	Recommends practical adaptations to the recruitment process itself to remove barriers to participation once recruitment has commenced, including multimodal outreach and community partnerships to reach underrepresented PWLE	[6, 9–11, 20, 21, 24, 25, 28, 30, 32, 34–36, 39, 42, 44, 45, 47, 49, 51, 54, 55, 57, 60]

Engagement strategies and motivations for participation

Guidance on meaningfully engaging and understanding why PWLE chose to participate in COS development was provided in 20 articles [6, 9, 11, 21, 24–26, 31–36, 39, 43, 50, 51, 54, 57, 60] (Table 4). This area of guidance recommends the use of PPI/PPIE (n = 6) [6, 25, 34, 35, 51, 57] and other patient-partners to facilitate meaningful engagement of participants more widely, for example, “Appoint[ing] a small number of Public Research Partners with lived experience of the condition of interest, an eagerness to express their opinions, and whom can provide continuity over a number of face-to-face workshops. A PPI/E Manager can be helpful in providing personal support and mentorship (to lived experience contributors” [35], p. 9). In addition, understanding the motivations for participation and tailoring retention and engagement activities to align with those motivations were consistently recommended across the 17 included papers [6, 9, 11, 21, 24–26, 32–34, 36, 39, 43, 50, 51, 54, 60]. One example related to involving children and young people as lived experience contributors and their motivations being “to participate in COS studies by feeling that they were making a valuable contribution; this seemed more important than financial incentives” ([33], p. 8).

Table 4.

Engagement strategies and motivations for participation

Sub-category	Code	Description	Contributing articles
Engagement strategies and motivations for participation (n = 20)	Motivational and relational strategies (n = 17)	Recommends understanding the motivations for participation and tailoring retention and engagement activities to align with those motivations	[6, 9, 11, 21, 24–26, 32–34, 36, 39, 43, 50, 51, 54, 60]
	Contextual adaptation strategies (n = 15)	Recommends tailoring engagement approaches to fit the practical and cultural context of interest-holders	[11, 21, 24–26, 31–35, 39, 43, 51, 54, 60]
	PPI-informed retention strategies (n = 6)	Recommends drawing on established PPI/PPIE literature to guide participant engagement and retention	[6, 25, 34, 35, 51, 57]

Promoting meaningful integration

Building on engagement strategies, twenty-seven articles [6, 9, 11, 21, 23–28, 30–32, 34–37, 39, 40, 42–44, 47, 49, 53–55] (Table 5) provided specific guidance on the pitfalls of tokenistic integration of PWLE, and strategies to avoid this through inclusive approaches to identify, recruit, retain, and integrate lived experience contributors. Guidance centred on implementing comprehensive methodological strategies for ensuring equity, diversity, and inclusion (EDI) throughout the identification, recruitment, and engagement processes. Adherence to EDI principles was found to help ensure authentic rather than superficial participation in all but two of the articles in this subcategory [23, 47]. Justifications for and reporting of EDI-related decisions are also recommended in half of the included articles in this category (n = 14) [6, 9, 11, 23–26, 30, 36, 37, 43, 47]. Methodological strategies to support EDI include providing sustained participation opportunities with multiple touch points, rather than one-time consultations [11], using transnational and transcultural recruitment practices [9, 39, 49], engaging PPI partners in the protocol development process [32], and adopting a broad perspective on who can be a lived experience contributor [49].

Table 5.

Promoting meaningful integration

Sub-category	Code	Description	Contributing articles
Promoting meaningful integration (n = 27)	EDI implementation strategies (n = 25)	Recommends implementing comprehensive methodological strategies for ensuring EDI throughout the COS development process; recommends adherence to EDI principles to ensure authentic rather than superficial participation; recommends providing sustained participation opportunities with multiple touch points rather than one-time consultations	[6, 9, 11, 21, 24–28, 30–40, 42–44, 49, 53–55]
	EDI decision documentation (n = 14)	Recommends justifying and reporting EDI-related decisions	[6, 9, 11, 23–26, 30, 32, 35–37, 43, 47]

Data collection considerations

The major category of “Data Collection Considerations” presents methodological guidance from all but four articles [38, 42, 46, 53] on gathering data that represent lived experience contributor perspectives in the long-list stage of COS development.

Primary data collection methods

Across the 31 articles [6, 9–11, 20–28, 30, 32, 33, 35, 36, 40, 43, 47–50, 52, 54, 56–60] (Table 6) included in this subcategory, guidance recommends selecting specific primary data collection methods based on research objectives. Online surveys are recommended when “… recruiting a large number of stakeholders internationally” ([27], p. 208). Focus groups and interviews are recommended when seeking to generate “a nuanced understanding of participant priorities and values that cannot be deduced from surveys” ([20], p. 225). One paper suggested that gathering data from participants directly (as in interviews or focus groups, etc.) allows researchers the flexibility to tailor methods to the population and/or context and encourages the participant to describe outcomes in their own voice [9].

Table 6.

Primary data collection methods

Sub-category	Code	Description	Contributing articles
Primary data collection methods (n = 31)	Interviews (n = 12)	Recommends using one-on-one interviews to allow flexibility in tailoring methods to population and/or context and to encourage participants to describe outcomes in their own voice	[6, 9, 10, 20, 22, 24, 27, 28, 30, 32, 48, 58]
	Focus groups and workshops (n = 21)	Recommends using focus groups and/or workshops when seeking group-based dialogue to explore shared priorities	[6, 9, 10, 20, 22, 24, 27, 28, 30, 32, 33, 35, 36, 48–50, 52, 54, 57, 58, 60]
	Surveys (n = 12)	Recommends using structured or semi structured questionnaires for broader input, especially when seeking diverse, large-scale international perspectives	[9, 20–24, 27, 28, 32, 40, 43, 47]
	Methodological guidance—general (n = 15)	Provides nonspecific recommendations related to designing or choosing primary data collection methods	[6, 9–11, 24–26, 28, 30, 32, 40, 48, 50, 56, 59]

Reviews and secondary data sources

Guidance on the use of existing evidence (reviews, databases, and routine data) as input on the perspectives of PWLE was provided in 16 articles [6, 9, 10, 23, 28–30, 35, 36, 44, 45, 48, 50, 56, 58, 59] (Table 7). Guidance was often related to the use of existing qualitative research, specifically, conducting qualitative evidence synthesis (QES) to generate outcomes for the long-list (n = 7) [6, 10, 30, 44, 48, 50, 56]. These approaches are recommended as ways to capture lived experience perspectives from previous research where interest-holders have shared their priorities and concerns. The guidance recommends using existing evidence over primary data collection when seeking a more practical alternative, not necessarily quicker but potentially more cost-effective [10]. Six articles [6, 29, 35, 36, 45, 50] recommended that a review of existing evidence can also include a review of patient-reported outcomes (PROs) and patient-reported outcome measures (PROMs). PROMs and PROs are positioned as useful alternatives to primary data collection, as the assumption is that they would be developed “with significant patient involvement” ([29], p. 9) and thereby contain what is important to service users [6].

Table 7.

Reviews and secondary data sources

Sub-category	Code	Description	Contributing articles
Reviews and secondary data sources (n = 16)	PROs/PROMs and external sources (n = 6)	Recommends reviewing PROs and PROMs as a useful alternative to primary data collection, as they are assumed to be developed with significant patient involvement and contain what is important to interest-holders	[6, 29, 35, 36, 45, 50]
	Qualitative evidence synthesis (n = 7)	Recommends these approaches to capture lived experience perspectives from previous research where interest-holders have shared their priorities and concerns	[6, 10, 30, 44, 48, 50, 56]
	Systematic reviews and scoping reviews (n = 10)	Recommends using structured reviews to identify outcomes from existing evidence	[6, 23, 29, 30, 35, 44, 50, 56, 58, 59]
	Reviews in general (n = 12)	Recommends using existing evidence over primary data collection when seeking a more practical alternative that is potentially more cost-effective	[6, 9, 10, 28–30, 36, 44, 48, 50, 56, 59]

Participatory methods and PPI/PPIE considerations

Sixteen articles [6, 9, 10, 25, 27, 32, 35, 36, 39, 47, 50, 51, 55, 57, 58, 60] (Table 8) recommend participatory approaches and public involvement to facilitate data collection in long-list development. While the benefits of PPI/PPIE were emphasised, guidance advises against its use as a substitute for qualitative methods used to elicit outcomes from PWLE [10]. Recommendations for PPI/PPIE and lay-researcher inclusion into the long-list process stress that it can be useful in maintaining the language of participants, refining and/or reducing the long-list prior to the consensus process, and providing a way for researchers and PWLE to work in a more cohesive and structured way [35].

Table 8.

Participatory methods and PPI/PPIE considerations

Sub-category	Code	Description	Contributing articles
Participatory methods and PPI/PPIE considerations (n = 16)	Participatory research methods (n = 4)	Recommends the use of coproduction, codesign, or other participatory research strategies	[27, 32, 36, 60]
	PPI/PPIE-facilitated representation (n = 9)	Recommends using PPI/PPIE to facilitate appropriate and diverse representation in data collection; cautions against using PPI/PPIE as a substitute for qualitative methods used in eliciting outcomes from PWLE	[9, 25, 32, 35, 47, 51, 57, 58, 60]
	PPI/PPIE-facilitated support and Capacity-Building (n = 4)	Recommends that PPI/PPIE can be used to develop relationships between community organisations, patient-advocacy organisations, and other groups where PWLE can be found	[25, 35, 39, 55]
	PPI/PPIE-facilitated flexibility and general advice (n = 8)	Recommends PPI/PPIE and lay-researcher inclusion to maintain the language of participants, refine and/or reduce the long-list prior to consensus, and provide a way for researchers and PWLE to work in a more cohesive and structured way	[6, 10, 32, 35, 50, 55, 57, 60]

Facilitators, training, and process adaptations

Twenty-eight articles [6, 9, 10, 20, 21, 23–25, 27, 30–32, 34, 35, 37, 39–41, 43, 45, 47, 48, 51, 54, 56–58, 60] (Table 9) were included in this subcategory. Using facilitators to act as liaisons between researchers and participants is recommended in one article [57], especially when neutral and independent interactions with PWLE are needed during the data collection process [57]. The guidance recommends that both researchers and those with lived experience need training and resources to support their understanding surrounding COS more broadly and specifics on how to elicit outcomes during data collection in the long-list period [41]. However, guidance advises caution in moderating the amount of training and education provided, as too much can “be detrimental and lead to patients disengaging… feeling overwhelmed or confused” ([9], p. 193).

Table 9.

Facilitators, training, and process adaptations

Sub-category	Code	Description	Contributing articles
Facilitators, training, and process adaptations (n = 28)	Facilitators and supports (n = 21)	Recommends using facilitators or other supports to act as liaisons between researchers and participants, especially when needing neutral and independent interactions with PWLE during the data collection process	[9, 20, 21, 24, 25, 27, 30, 32, 34, 35, 37, 39, 41, 43, 45, 47, 51, 54, 57, 58, 60]
	Training and education (n = 13)	Recommends that both researchers and those with lived experience receive training and resources to support their understanding of COS and how to elicit outcomes during data collection; advises caution in moderating the amount of training to avoid overwhelming or confusing participants	[9, 24, 25, 34, 37, 39, 41, 43, 47, 51, 54, 58, 60]
	Tailoring and process communication (n = 20)	Recommends tailoring data collection methods to population and/or context and to adapt how the process and outcomes are discussed with participants based on condition, population, or setting	[6, 9, 10, 20, 23, 25, 30–32, 35, 37, 40, 41, 43, 47, 48, 54, 56, 58, 60]

Analysis and reporting

This category captures methodological guidance on analysing, validating, and reporting outcomes derived from lived experience perspectives in COS development. All but 13 articles are included in this major category [11, 31, 33, 38, 39, 41, 43, 45, 49, 51, 52, 57, 60].

Analysis methods

This subcategory encompasses methodological guidance on selecting, implementing, and optimising qualitative analytical approaches for identifying and refining outcomes from data collected reflecting lived-experience perspectives during long-list development. Twenty-four articles were included in this subcategory [6, 9, 10, 20–24, 27–30, 32, 35, 36, 40, 42, 44, 48, 50, 55, 56, 58, 59] (Table 10). The guidance recommends selecting analytical methods to best suit the type of data obtained in the collection stage and tailoring analysis to the aim of generating outcomes in the long-list stage [30, 40]. Specific methodological recommendations include using thematic analysis (n = 5) [27, 35, 42, 58, 59] and content analysis (n = 2) [21, 29]. Mixed methods approaches are also recommended (n = 19) [6, 9, 10, 20, 22–24, 28–30, 35, 36, 40, 42, 44, 48, 50, 58, 59] including structuring analysis to existing frameworks [6, 45, 56].

Table 10.

Analysis methods

Sub-category	Code	Description	Contributing articles
Analysis methods (n = 24)	Specific methods used in data analysis (n = 10)	Recommends using thematic analysis, content analysis, and framework-based analysis approaches	[6, 21, 27, 29, 35, 42, 44, 56, 58, 59]
	The use of qualitative analysis methods in general (n = 18)	Recommends selecting analytical methods to best suit the type of data obtained in the collection stage and to the aim of generating outcomes in the long-list stage	[6, 9, 10, 20–24, 30, 32, 35, 36, 40, 44, 48, 55, 56, 58]
	Leveraging existing qualitative evidence (n = 8)	Recommends incorporating preexisting qualitative research to identify patient-centred outcomes without duplicating research efforts through qualitative evidence synthesis approaches	[6, 10, 30, 42, 44, 48, 50, 56]
	Mixed-methods analysis methods (n = 19)	Recommends using mixed methods approaches for analysing collected data	[6, 9, 10, 20, 22–24, 28–30, 35, 36, 40, 42, 44, 48, 50, 58, 59]

Transparency and validation

This subcategory captures methodological guidance on ensuring transparency, credibility, and contextual clarity during outcome identification, analysis, and systematic reporting when incorporating lived experience perspectives into the COS development process. Twenty-two articles were included in this subcategory [6, 10, 20, 21, 24–27, 29, 30, 34, 36, 37, 40, 42, 44, 46, 48, 50, 55, 58, 59] (Table 11). The guidance provided emphasises the need to justify analytic decisions, maintain rigour in validation procedures, and support transferability, e.g. the ability to apply a COS across different populations, settings or contexts, and future refinement of COS, e.g. the iterative updating and improvement of COS as new evidence emerges. Several articles (n = 17) [6, 9, 10, 20, 24–27, 29, 34, 37, 40, 42, 44, 50, 58, 59] provide recommendations related to this, such as clear reporting of the aims, topic guides used in primary data collection methods, justifications for analysis methods, and “overt description of findings” throughout the COS development process ([40], p. 13). Recommendations include incorporating and following established reporting frameworks for COS development and reporting, including guidance from the COMET Initiative [6, 46], such as the Core Outcome Set–STAndards for Reporting (COS-STAR) statement [61] alongside the Consensus-based Standards for the selection of Health Measurement Instruments (COSMIN) [62]. Guidance also highlights that “… different methodological decisions can make a substantial impact on the identification of potential core outcomes.” ([59], p. 1482).

Table 11.

Transparency and validation

Sub-category	Code	Description	Contributing articles
Transparency and validation (n = 22)	Explaining methods and decisions (n = 15)	Recommends clearly reporting aims, topic guides used in primary data collection methods, and justifications for analysis methods; recommends providing clear description of findings throughout the COS development process	[6, 9, 10, 20, 21, 24–27, 29, 30, 36, 40, 55, 59]
	Checking accuracy and relevance (n = 17)	Recommends justifying analytic decisions and maintaining rigour in validation procedures by incorporating and following established reporting frameworks including COS-STAR, COSMIN, and COMET Initiative guidance	[6, 9, 10, 20, 24–27, 29, 34, 37, 40, 42, 44, 50, 58, 59]
	Improving or adding to existing COS (n = 8)	Recommends demonstrating how existing outcome sets can be expanded when gaps are identified	[6, 10, 27, 40, 42, 44, 46, 48]

Preserving PWLE perspectives

With 22 included articles [6, 9, 10, 20, 22, 24, 25, 27, 28, 30, 32, 35, 40, 42, 44, 46, 47, 53–56, 58] (Table 12), this subcategory addresses strategies for ensuring that the perspectives of PWLE remain central during analysis through predetermined epistemological and theoretical decisions made at the protocol stage. It includes methods to protect the authenticity of contributions, linking analytic choices to explicit philosophical approaches and broader theoretical goals, and engaging PPI/PPIE partners meaningfully in interpreting and shaping findings. PPI/PPIE is recommended as a method for condensing the long-list period before consensus and to make the long-list more relevant and manageable, better reflecting the language of PWLE [9]. Key methodological recommendations emphasise the preservation of the authentic voice and priorities of PWLE [27, 35]. Qualitative methods are recommended to ensure that the “long lists of outcomes that go forward to a consensus process are comprehensive from the perspective of the whole community of relevant stakeholders, not just the groups that have historically influenced what outcomes are measured in research” ([6], p. 26).

Table 12.

Preserving PWLE perspectives

Sub-category	Code	Description	Contributing articles
Preserving PWLE perspectives (n = 22)	Preserving authentic language and terminology (n = 22)	Recommends using participants’ own words when possible, ensuring language is understandable to diverse interest-holder groups, and reducing researcher bias or interpretation that may distort lived experience	[6, 9, 10, 20, 22, 24, 25, 27, 28, 30, 32, 35, 40, 42, 44, 46, 47, 53–56, 58]
	Purpose-driven methods (n = 17)	Recommends linking analytic choices to explicit philosophical approaches and broader theoretical goals; recommends making predetermined epistemological and theoretical decisions at the protocol stage to ensure PWLE perspectives remain central during analysis	[6, 10, 20, 22, 25, 27, 28, 30, 32, 40, 42, 46, 47, 54–56, 58]
	PPI/PPIE-mediated analysis considerations (n = 5)	Recommends involving PPI/PPIE partners in reviewing, interpreting, or co-analysing findings to ensure lived-experience perspectives are accurately represented and prioritised during analysis	[6, 10, 22, 32, 56]

Contextual considerations

The major category of “Contextual Considerations” captures methodological guidance concerning broader contextual factors that shape the inclusion of PWLE in the long-list generation. All but five of the articles in this review are included in this major category [22, 23, 29, 31, 59]. The articles describe structural, sociocultural, logistical, and ethical issues that influence method design and implementation.

Engaging non-traditional populations and contexts

This subcategory reflects guidance on working with populations and settings that may require methodological adaptation owing to factors such as participant age, participant capacity, marginalisation, or geographical and socioeconomic context. All bar 10 of the articles in this major category are included in this subcategory [9, 27, 28, 35, 36, 41, 45–47, 51] (Table 13). Articles recommended approaches for working with populations with specific needs and/or populations traditionally excluded from healthcare research (n = 22) [6, 10, 11, 21, 24–26, 30, 32–34, 37, 38, 40, 43, 48–50, 53, 55, 57, 58] and/or those across varied geographic, cultural and/or socioeconomic settings (n = 19) [11, 20, 21, 24, 25, 32, 37, 39, 40, 42, 44, 49, 50, 52, 54–56, 58, 60]. Key recommendations to do so included the use of strategies to maximise regional, cultural, and economic diversity in participants with the aim of addressing structural inequality and other issues potentially impacting who is involved in COS development [11, 37]. The guidance recommends developing a broad and representative outreach strategy to “assure that people who need to be in the room or need to know about will be invited to be in the room are there” ([25], p. 146). In addition, guidance advises that developers seeking diverse representation must also consider the potential for harm and the amount of emotional labour that can follow the inclusion of special groups such as children, survivors, and those with cognitive challenges [48, 50].

Table 13.

Engaging non-traditional populations and contexts

Sub-category	Code	Description	Contributing articles
Engaging non-traditional populations and contexts (n = 30)	Marginalised and vulnerable Groups (n = 14)	Recommends developing broad and representative outreach strategies to maximise inclusion of individuals and communities affected by structural disadvantage or social exclusion	[6, 10, 11, 21, 24, 25, 32, 37, 40, 43, 48, 50, 57, 58]
	Proxy and developmental interest-holders (n = 12)	Recommends considering inclusion of family members, caregivers, or others speaking on behalf of those unable to participate directly (e.g. young children, cognitively impaired individuals)	[24, 26, 30, 32–34, 37, 38, 49, 53, 55, 58]
	Diverse and global contexts (n = 19)	Recommends maximising regional, cultural, and economic diversity in participants to address structural inequality; recommends ensuring outreach strategies incorporate varied geographic and socioeconomic settings including LMIC contexts	[11, 20, 21, 24, 25, 32, 37, 39, 40, 42, 44, 49, 50, 52, 54–56, 58, 60]

Balancing comprehensiveness with practical constraints

This subcategory includes 16 articles [9–11, 25, 28, 33, 35, 37, 39, 41, 42, 50, 52, 56, 57, 60] (Table 14) discussing the challenge of developing a comprehensive long-list of outcomes that adequately captures lived experience perspectives with often limited resources and/or how to manage resources or logistical obstacles. Eleven articles [10, 11, 25, 28, 33, 35, 39, 50, 52, 57, 60] recommend strategies for managing funding and/or other monetary challenges, including planning for additional funding at the protocol stage of COS development to support meaningful participation of PWLE via adequate compensation, addressing accessibility concerns, and tailoring recruitment strategies. Others (n = 7) [9, 10, 25, 37, 50, 56, 57] recommend being balanced in the approach to resource use; using enough resources for the most benefit as a “trade-off between what would be ideal and what was pragmatic” ([25], p. 147).

Table 14.

Balancing comprehensiveness with practical constraints

Sub-category	Code	Description	Contributing articles
Balancing comprehensiveness with practical constraints (n = 16)	Time and financial constraints (n = 15)	Recommends planning for additional funding at protocol stage to support meaningful participation through adequate compensation and accessibility accommodations	[9–11, 25, 28, 33, 35, 37, 39, 42, 50, 52, 56, 57, 60]
	Systems and infrastructure limitations (n = 11)	Recommends balancing comprehensiveness with pragmatism as a “trade-off between what would be ideal and what was pragmatic” [25, p. 147]; recommends allocating sufficient resources to maximise benefit	[10, 11, 25, 28, 37, 41, 42, 52, 56, 57, 60]

Tailoring methods to participant needs and modalities

This subcategory captures methodological adaptations required to accommodate PWLE and their unique needs to ensure meaningful participation in long-list development. Twenty-six articles [11, 20, 21, 24, 25, 27, 30, 32, 35–38, 41, 43, 45–52, 54, 55, 57, 60] (Table 15) provided guidance on adapting language, format, pacing, and mode of engagement (e.g. in-person, online, telephone) to suit participant preferences and capabilities. Guidance recommends using “lay language” [51, p. 945] whenever possible, keeping in mind that accessible language helps to enable an outreach strategy that builds diverse perspectives [21]. In addition, guidance recommends that the use of technology should not be overlooked as a way to improve diverse perspectives, although guidance suggests that technology should be piloted and/or validated, possibly by using PPI/PPIE contributors in the process [41].

Table 15.

Tailoring methods to participant needs and modalities

Sub-category	Code	Description	Contributing articles
Tailoring methods to participant needs and modalities (n = 26)	Language and communication accessibility (n = 15)	Recommends using lay language whenever possible; recommends adapting language, format, and pacing to suit participant preferences and capabilities	[11, 20, 24, 25, 27, 30, 37, 41, 45–47, 51, 52, 55, 57]
	Technology use for inclusion (n = 14)	Recommends considering technology as a tool to improve diverse perspectives; recommends piloting and/or validating technological approaches	[11, 21, 24, 27, 32, 35, 37, 41, 48–50, 54, 57, 60]

Ethical and philosophical foundations of inclusion

This subcategory reflects ethical and philosophical guidance for ensuring that the inclusion of PWLE is meaningful, values-driven, and just. Twelve total articles [6, 9, 25, 27, 32, 35, 43, 47, 48, 50, 52, 57] (Table 16) provided guidance and reflections surrounding the ethical considerations and implications of the long-list development process and of participant representation and inclusion in general. Across the articles, the issue of whether ethics approval is “needed” is considered frequently; the barriers of time and other resource constraints are discussed; however, one article highlighted the “balance” sometimes needed within ethics and COS development, “… the practicalities surrounding ethics approvals rather than research principles are shaping how COS development is conceptualised” ([25], p. 146). Another provides a call to action, “… the onus is on the COS development community to address these (ethical) issues and enable patients to participate meaningfully” ([43], p. 414).

Table 16.

Ethical and philosophical foundations of inclusion

Sub-category	Code	Description	Contributing articles
Ethical and philosophical foundations of inclusion (n = 12)	Avoiding tokenism and promoting meaningful engagement (n = 11)	Recommends ensuring inclusion of PWLE is meaningful, values-driven, and just	[9, 25, 27, 32, 35, 43, 47, 48, 50, 52, 57]
	Ethical grounding for methodological choices (n = 11)	Recommends reporting justification of methodological decisions based on ethical principles or frameworks	[6, 25, 27, 32, 35, 43, 47, 48, 50, 52, 57]
	Equity in decision-making processes (n = 5)	Recommends ensuring inclusive, transparent, and fair interest-holder decision-making throughout the process	[25, 27, 35, 47, 52]

Discussion

This scoping review addresses a gap in COS development by identifying methodological guidance on incorporating lived experience perspectives into the early long-list stage. From 45 articles, we developed four categories of guidance: (1) PWLE Identification, Recruitment, and Engagement; (2) Data Collection Considerations; (3) Analysis, Validation, and Reporting Considerations; and (4) Contextual Considerations. These results highlight an evolving methodological landscape surrounding lived experience contributor perspective integration into COS development. Our results align with broader movements within the healthcare research landscape, where PWLE have largely been omitted from project development or limited to consultant roles [63, 64], and reflects wider calls for the use of qualitative and participatory methods and person-centred research approaches [65–67]. Overall, the guidance highlights a growing recognition that meaningful lived experience integration requires deliberate and rigorous methodological choices [67, 68].

A notable characteristic of the guidance identified in this review is that much of it echoes broader principles of inclusive and participatory research practice [65–67]. While many recommendations align with wider participatory research guidance, within the included studies these principles were applied specifically to methodological decisions made during long-list development, including defining relevant lived experience perspectives, eliciting outcome-focused data and translating participant language into outcomes, and validating outcome relevance and interpretation.

Recommendations for PWLE identification, recruitment, and engagement

• Establish operational definitions for “lived experience” at the protocol stage and provide clear justification for the inclusion criteria;

• Develop recruitment strategies tailored to the COS aims;

• Consider multiple touch points rather than one-time consultations with PWLE to avoid tokenistic participation.

Included studies consistently positioned purposeful and transparent planning for PWLE identification, recruitment, and engagement as foundational to the long-list process (detailed in section “PWLE identification, recruitment, and engagement”). Across both COS development and the wider literature, there have been repeated calls for predefined recruitment methods and transparent decision-making, reflecting broader open-science principles [69, 70].

The guidance also reinforces COMET’s recommendation to preregister COS projects [6], which may enhance transparency and allow for wider scrutiny of long-list development processes and resulting outcome selection [6, 61]. More broadly, our findings are consistent with established frameworks for meaningful interest-holder engagement across health research, which increasingly recognise that representativeness must be purposeful, intentional, and adequately resourced rather than assumed in health research [62, 71, 72].

Recommendations for data collection

• Methodological flexibility is needed to balance comprehensiveness of the included perspectives with practical considerations of resource constraints;

• Multiple methods of data collection (e.g. primary qualitative, surveys, secondary data analysis) should be used in a complementary and purposeful manner;

• Adequate and targeted training for all, including researchers, participants, and research partners.

The breadth of data collection guidance identified in this review (detailed in section “Data collection considerations”) reflects the complexity of generating comprehensive long-lists that meaningfully incorporate lived experience perspectives. Included studies recommended methodological flexibility in order to balance breadth and diversity of perspectives with available resources, timelines, and expertise. Use of multiple data collection approaches in a complementary and purposeful manner, including primary qualitative methods, surveys, and secondary data analysis, was commonly advised, alongside adequate and targeted training for researchers, participants, and research partners. Pragmatic approaches to data collection were advised when aiming to elicit lived experience contributor perspectives. This emphasis on methodological flexibility likely reflects recognition that, even within a single healthcare condition, lived experience perspectives may vary considerably across individuals and contexts. Consequently, data collection approaches may need to be adapted to the characteristics, preferences, and capacities of the population involved, while remaining aligned with the aims of the COS. Such decisions are consistent with established qualitative and mixed-methods approaches in healthcare research, where methodological adaptation is often necessary to support inclusivity, accessibility, and meaningful participation [73]. Resource limitations were frequently cited as drivers of data collection decisions [9–11, 28, 33, 35, 37, 39, 41, 42, 50, 52, 56, 57, 60, 74], underscoring the need to plan data collection methods in line with available time, expertise, and funding.

Recommendations for analysis and reporting

• Preserve, whenever possible, the language/words used by lived experience contributors throughout the process;

• Document all methodological choices in analysis, provide clear justification for those choices, and validate those choices via participants and/or PPI partners;

• Utilise existing reporting frameworks (COS-STAR⁶¹, COS-STAD⁴⁶, SRQR⁷⁵, COREQ⁷², etc.) as appropriate.

The analysis and reporting guidance identified in this review (reported in section “Analysis and reporting”) converges on an overarching principle: the integrity of lived experience perspectives must be actively protected throughout the analytical process. This includes preserving the voices, words, and languages of PWLE whenever possible in analysis and reporting; clearly documenting and justifying methodological decisions; validating interpretations with participants or PPI partners; and using established reporting frameworks such as COS-STAR [61], COS-STAD [46], Standards for Reporting Qualitative Research (SRQR) [75], and Consolidated Criteria for Reporting Qualitative Research (COREQ) [72]. Preserving the “authentic voice” of PWLE in the long-list stage of COS development aligns with established principles in qualitative and participatory action research (PAR) methods [76]. Utilising existing methodological guidelines to support rigour in qualitative analysis and those for participatory research methods can therefore aid in the development of the long-list. Our findings also highlight the risk of “qual-light” approaches within COS development, where qualitative methods may be used without sufficient methodological rigour or reporting transparency [77, 78]. This concern reflects broader critiques of mixed-methods research in which qualitative approaches are incorporated into predominantly quantitative paradigms without full adherence to qualitative standards [77, 78]. Existing reporting guidance may therefore support greater rigour and transparency in long-list development. While COS-STAR, COS-STAD, and COSMIN provide useful direction within COS research, qualitative and PPI-specific reporting frameworks such as COREQ, SRQR, and GRIPP2 may be particularly valuable when reporting lived experience involvement and qualitative analytical processes [15, 46, 61, 62, 72, 75]. The increasing availability of reporting frameworks across health research also reflects the interdisciplinary nature of COS development, with resources such as the EQUATOR Network offering useful guidance for selecting appropriate frameworks [79].

Equity, diversity, and inclusion recommendations

• Address systemic barriers to participation to support meaningful inclusion;

• Proactively engage with non-traditional clinical research populations and employ flexible engagement modalities to aid in participation;

• Ensure that ethical standards are maintained and view inclusion as essential rather than optional;

• Monitor and reevaluate plans and procedures throughout the process; monitor retention and metrics; and note to what extent lived experience perspectives have influenced the process.

The contextual considerations guidance presented in section “Contextual considerations” reflects a growing consensus that meaningful inclusion of PWLE perspective requires structural and methodological adaptation, not a simple aspiration toward diversity. The guidance recommended addressing systemic barriers that hinder participation, proactively engaging with non-traditional clinical research populations via flexible modalities, upholding ethical standards while viewing inclusion as a necessity, and continuously monitoring and reevaluating plans and procedures, including retention metrics and the impact of lived experience perspectives throughout the process.

EDI principles provide a useful foundation for all aspects of the long-list development process [80, 81]. Our results support the need for purposeful and reflexive planning with the goal of enacting EDI principles from the beginning of the COS process and that methodological decisions reflect the needs of PWLE. Tailored recruitment, data collection, and analysis processes should support the meaningful inclusion of those most affected by the resulting COS in the long-list development process. These results align with recent literature suggesting that embedding EDI requires structural adaptation, not just personal reflection [80]. Gedela et al. [82] further argued that EDI frameworks should be embedded throughout health research design, conduct and implementation to help mitigate power imbalances and systemic barriers to engagement.

Critically, EDI considerations can move beyond determining “who” should be included but also “how” and “why” their participation is (should be) supported and reported [83, 84]. Our results on contextual considerations reinforce this point. The inclusion of historically excluded groups in health research requires first understanding why these groups were excluded and how to address the barriers that led to their exclusion [83, 84]. Our practical recommendations aid in addressing some of these challenges by emphasising the need for proactive, reflexive, and purposeful decisions, including full engagement with ethical standards.

Other considerations: moving beyond PPI conventions

PPI and PPIE were mentioned frequently across the included articles and were often cited as being central to providing context to COS developers when seeking to validate lived experience perspectives in the long-list stage [34, 51, 58]. The results of this review recognise the importance of PPI/PPIE, but caution is needed to ensure that it is not a replacement for lived experience contributor participation in the long-list process [33]. In addition, some traditional PPI and PPIE approaches can reinforce power imbalances and systemic barriers to meaningful inclusion rather than address them in this long-list stage by focusing on consultation and feedback as opposed to the generation of new outcomes within COS development [85, 86]. The guidance provided across the included articles encouraged PPI practices to go deeper, if included in the long-list stage, where public partners would also be involved in methodological decisions (e.g. how to elicit lived experience perspectives or recruitment and retention plans) rather than limiting them solely to validation and/or refinement of the long-list prior to consensus [34, 51, 58].

Implications for future research

The concentration of included literature within high-income, English-language contexts represents a significant gap with direct implications for the EDI principles that the guidance itself highlights. Future research should explicitly address whether the recommendations identified in this review are applicable across diverse cultural, linguistic, economic, and healthcare system contexts, with particular attention to low- and middle-income country settings where COS development activity is increasing [11, 37].

The guidance identified in this review relies on reporting frameworks developed outside the COS space, including COREQ [72], SRQR [75], and GRIPP2 [15]. While these frameworks provide useful scaffolding, they were not designed with the specific methodological challenges of the long-list stage in mind. Future research could explore whether long-list-specific reporting guidance, potentially developed as an extension of or complement to existing COS reporting standards such as COS-STAR [61] and COS-STAD [46], would strengthen methodological transparency and consistency across the field.

Finally, the empirical validation of the recommendations presented in this review is an identified priority. Qualitative and mixed-methods research with COS developers and PWLE, focusing on the rationale for methodological decisions made at the long-list stage and the experiences of those involved, would provide the nuanced, context-specific evidence needed to refine and strengthen the guidance identified here.

Limitations and strengths

Limitations of the evidence base

Some recommendations were generated based on empirical research methods and reviews of research, whereas others are commentaries and opinion pieces. In addition, the distribution of articles across multiple clinical and/or topic areas suggests that methodological guidance on this topic has emerged organically across disciplinary boundaries rather than within a single domain. This heterogeneity of included articles means that not all guidance carries equal weight, and readers should carefully consider the specific source context when incorporating identified guidance into their own COS development processes.

The concentration of included articles within a relatively small number of specialist journals and institutions, particularly the University of Liverpool and the COMET Initiative, suggests that much of the methodological development in this area has emerged from a limited number of established research groups.

COS development is growing rapidly, with additional COS and COS-related publications being added to the COMET Database regularly [7]. As previously mentioned, gaps in the methodological guidance identified in earlier articles were often addressed in later articles. This rapid proliferation of articles and heterogeneity of sources may mean that relevant articles were not identified via the search strategies used in this review. Articles reporting successful, novel approaches may be more likely to be published than those documenting challenges. Despite the comprehensive search strategies used in this review, relevant articles and/or those reporting novel and/or unsuccessful approaches may have been missed and therefore not included. The heterogeneity of the articles could also contribute to challenges across the analysis stage of this review.

Limitations of the review process

The articles included in this review were limited to those written in English. COS development practices have been increasing across cultural, economic, and geographic boundaries. The exclusion of non-English language articles potentially limits the scope of this review, including the potential to identify guidance that is specific to non-English language contexts. This limitation is especially challenging to justify given the depth of guidance identified on the importance of incorporating EDI practices into the COS development process.

Additionally, brief or incidental methodological guidance embedded within full texts may not always be signalled in titles or abstracts; while our dual-reviewer screening process, exhaustive citation searching, and expert consultation mitigated this risk, some relevant guidance may not have been identified. Our synthesis process was iterative and involved some level of interpretation for ease of reporting; the necessary interpretation required to categorise diverse data sources may have introduced a degree of researcher bias, which we mitigated through regular independent reviewer consensus meetings. Our analysis process may have inadvertently emphasised some perspectives or minimised others.

Strengths

Despite these limitations, this review has several notable strengths. To our knowledge, this is the first review of the COS literature to focus on lived-experience inclusion in the long-list stage of development. Our search strategy was developed in consultation with a health research librarian and through expert consultation with COS specialists. In addition, we purposefully included both peer-reviewed and grey literature across multiple databases and the entirety of the COMET Database to help ensure that all relevant literature was identified.

Our methods followed established guidance from JBI and PRISMA-ScR, supporting transparency and reproducibility [13, 14]. The involvement of multiple reviewers throughout the screening, extraction, and analysis processes is a strength [87]. Additionally, the inclusion of a PPI partner from inception to dissemination ensured that our review remained grounded in the perspectives of PWLE of clinical research practice and their priorities [88]. Using both deductive and inductive coding enabled a systematic, iterative analysis that produced actionable guidance and theoretical insights to support future COS development.

Conclusions

This review charted an emerging, nuanced, and sometimes fragmented body of literature. It highlighted the challenges that COS developers face when seeking best practice recommendations on including the perspectives of PWLE into the long-list stage of COS development. We provide a comprehensive collection and synthesis of recommendations across a wide body of literature, in addition to practical recommendations for future COS development work. The findings underscore the need for additional research into transparent, purposeful, and EDI-driven methodological approaches to lived experience contributor participation in the development of COS. We have set the foundation for future empirical work into these best practices and, in doing so, aim to support broader goals of enhancing the relevance, inclusivity, and impact of COS within health research.

Abbreviations

COS

Core Outcome Set or Core Outcome Sets

PWLE

People with lived experience

OMERACT

Outcome Measures in Rheumatology

COMET

Core Outcome Measures in Effectiveness Trials

PPI/PPIE

Patient and Public Involvement/Patient and Public Involvement and Engagement

JBI

Joanna Briggs Institute

PRISMA-ScR

Preferred Reporting Items for Systematic Reviews and Meta-Analyses extension for Scoping Reviews

GRIPP2-SF

Guidance for Reporting Involvement of Patients and the Public, Short Form

PRESS

Peer Review of Electronic Search Strategies

LMICs

Low- and Middle-Income Countries

EDI

Equity, Diversity, and Inclusion

QES

Qualitative Evidence Synthesis

PROs

Patient-Reported Outcomes

PROMs

Patient-Reported Outcome Measures

COS-STAR

Core Outcome Set–STAndards for Reporting

COSMIN

Consensus-based Standards for the Selection of Health Measurement Instruments

SRQR

Standards for Reporting Qualitative Research

COREQ

COnsolidated Criteria for REporting Qualitative Research

PAR

Participatory Action Research

EQUATOR

Enhancing the Quality and Transparency of Health Research Network

HRB-TMRN

Health Research Board – Trials Methodology Research Network

Authors’ contributions

All the authors contributed to the conceptualisation of this review question. MKL drafted the manuscript and is the guarantor of this manuscript. KR and ET contributed critical insights during the design phase and reviewed and revised the manuscript for important intellectual content. All authors read and approved the final version of the manuscript.

Funding

This research forms part of a doctoral research project supported by the Health Research Board Trials Methodology Research Network (HRB-TMRN) PhD scholarship awarded to ML. The funder had no role in the design, data collection, and analysis or preparation of the protocol.

Data availability

All completed data extraction forms and analysis files are available from the corresponding author upon request.

Declarations

Ethics approval and consent to participate

Not applicable.

Consent for publication

Not applicable.

Competing interests

The authors declare no competing interests.