Pathways to Equitable Access to Kidney Transplantation in Spain (PATH2KT): A Transformative Mixed-methods Study Protocol

METHODS AND ANALYSIS >> Study design The design of this research protocol follows the premises of the mixed-methods approach under the transformative paradigm 26,27. This means that various phases of data collection -both quantitative and qualitative- will be conducted, analyzed separately, and then integrated through methodological triangulation to corroborate and enrich the findings 28. The research will be centered on social justice, amplifying the voices of communities facing health inequalities or treatment deprivation. Using the transformative mixed-methods approach, different power structures that may be involved in the results will be analyzed and linked to actions that promote equity, ultimately providing a report with recommendations for action based on the results obtained 26,27. The achievement of results under this methodology and paradigm will be accomplished through various research phases, explained in detail below.

This protocol follows the Good Reporting of A Mixed Methods Study (GRAMMS) guidelines, recognized for ensuring high-quality evidence-based methodology 29.

• Patient and public involvement This protocol has been reviewed and endorsed by the CKD community in Spain, including the National Federation of Associations for the Fight Against Kidney Diseases (ALCER) and the ADER Foundation (Kidney Patients Association of Catalonia). These organizations will actively support the dissemination of the study in different regions and will facilitate recruitment of participants during the data collection phase. Moreover, patient representatives will be involved in the interpretation of findings, ensuring that the analysis incorporates lived experiences and enhances the relevance and clarity of results.

• Study setting and context The data collection components of this research protocol will be conducted in Spain, a high-interest setting for the care of people with CKD. Spain's healthcare system is public and universal, primarily funded through taxes, ensuring healthcare access for the entire population, including individuals requiring KT 30. The country is internationally recognized for its high rates of organ donation and transplantation, supported by the Spanish National Transplant Organization (Organización Nacional de Trasplantes, ONT), which emphasizes coordination, regulation, and public engagement 31. Spain's healthcare system is also highly decentralized, with responsibilities for healthcare planning, service delivery, and resource allocation delegated to the 17 autonomous regions. This structure includes regional transplant coordination offices that work in alignment with the ONT to implement national policies at the local level, but may also reflect regional specificities and priorities. Despite this strong institutional framework, inequities in KT access might arise from factors such as socioeconomic status, geographic area and interregional differences linked to the decentralized organization of the healthcare system. By focusing solely on the Spanish context, while allowing for international discussion across the proposed phases, this study seeks to generate detailed insights and propose actionable recommendations grounded in the realities of Spain's healthcare infrastructure and sociopolitical landscape.

• Data collection and analysis Data collection and analysis will be carried out using a mixed approach, combining both quantitative and qualitative methods. This will result in four distinct research phases, tailored to the specific objectives of this research protocol.

• Phase 1. Literature review The first phase of this study aims to address objectives 1 and 2, which focus on synthesizing and critically appraising the existing literature on instruments and variables used to evaluate inequities among individuals with CKD, as well as on examining how unequal access to KT is described and explained. To achieve this, two systematic reviews will be conducted.

Both reviews will be carried out following the methodological recommendations of the Joanna Briggs Institute (JBI) and will be reported according to the PRISMA 2020 guidelines 32,33. The protocols for the reviews will be registered in PROSPERO®. Searches will be conducted in the major electronic databases, using controlled vocabulary (MeSH) and will include peer-reviewed studies published between 2015 and 2025 in English, Spanish, French, or Portuguese. Eligibility criteria will be based on the PICOT framework, and include quantitative, qualitative, and mixed-methods research, as well as systematic and scoping reviews. Study selection, data extraction, and critical appraisal will be carried out independently by two or more reviewers, with discrepancies resolved by consensus or consultation with a third reviewer. Covidence® software will be used to manage the workflow.