Work

Understanding underserved and underrepresented populations in European clinical studies: a narrative review with systematic approach

Year: 2026

Type: review

Abstract: Ensuring inclusivity in clinical research has become both a scientific and ethical imperative. Representative participation in clinical studies is essential for greater generalizability and equitable applicability of research findings. Persistent exclusion of underserved (US) and underrepresented (UR) groups in clinical studies continues despite ongoing regulatory efforts across Europe and beyond to address this issue. Yet ambiguity persists around how US/UR populations are defined, limiting progress towards achieving more representative, inclusive and equitable clinical research. This review aims to understand how US/UR populations in European clinical studies are presented in literature, identify common descriptors and definitions, and examine which groups are labeled as US/UR in order to inform efforts to enhance inclusion and equitable representation of these populations in research. A narrative literature review with a systematic approach was conducted, in line with PRISMA guidelines. PubMed and Psycinfo/PsycArticles databases were searched for articles published between 2014 and 2024, including characterizations of US/UR populations in European clinical studies, yielding 5413 articles. Data were extracted on definitions, descriptors, and identified US/UR populations within clinical research, with attention to geographic context and barriers to inclusion. Following screening, 62 full-text publications were included. Most articles reported findings from the U.K. ( n = 29) or from international contexts ( n = 20), while only five articles focused on EU countries. About one-third of the reviewed articles ( n = 21) provided some definitions/descriptions of US/UR populations, whereas most relied on descriptors or group examples. Race and ethnicity were the most frequently cited descriptors followed by socioeconomic status (SES), age, geographic location, health status, disability, language, sex, and gender. Across clinical studies, several recurring groups emerged, that were organized in four overarching categories: demographic, socioeconomic and geographic, health-status and access-related, and those shaped by contextual or systemic exclusion. The findings of this review point to a clear gap in the current literature regarding explicit characterizations of US/UR populations in clinical studies in Europe. Current ways of describing these groups lack contextual grounding and consistent application, limiting their usefulness for promoting data-driven inclusivity. To this aim, context-specific characterizations and adherence to reporting standards are needed to guide equitable representation in clinical research. This review informs the IHI READI consortium’s mission and efforts to foster a more representative, inclusive and patient-centered European research ecosystem.

Source: Trials

DOI: 10.1186/s13063-026-09989-6