Background: The underrepresentation of minority populations in clinical trials and observational studies has recently been documented, such that the results obtained are in some cases not truly generalizable to the majority population, limiting the extrapolation of results to all patients. In rheumatic diseases, this inequality in access to clinical studies has also been documented, although available data are still very limited.

Objectives: To study the representativeness of the different nationalities of patients participating in clinical studies (PPCS) compared with the overall group of patients in routine clinical practice (PRCP) in a tertiary hospital.

Methods: A retrospective observational study was conducted including patients with rheumatic diseases who voluntarily participated and provided informed consent in clinical studies (observational study or clinical trial) between 2014 and 2025, from whom nationality and sex data were collected. Data from patients followed in Rheumatology outpatient clinics in PRCP with the same diagnoses as the PPCS during the same period were used as a comparison group.

Results: Data from 5,577 patients were included: 4,692 PRCP and 885 PPCS. The diagnoses represented in PRCP were: 31.61% rheumatoid arthritis (RA), 19.25% spondyloarthritis (SpA), 17.48% psoriatic arthritis (PsA), 14.15% polymyalgia rheumatica (PMR), 9.19% Sjögren’s syndrome (SS) and 8.33% systemic lupus erythematosus (SLE), and. No significant inequalities were observed in the proportion of foreign nationality between PPCS and RCPC patients. When classifying foreign nationalities by region of origin, the most represented were South America (7.98% of total RCPC) and Europe (3.09%). No significant differences were observed between both groups, except for the African-origin population (table 1).

In the most representative foreign populations, when comparing by diagnosis, the representativeness of these nationalities in PPCS with respect to RCPC is maintained (table 2). However, in the group of patients with SS and SLE, differences are observed, since no patients with SS and a lower proportion of patients with SLE of non-Spanish nationality participated in a clinical study. In addition, among patients diagnosed with SpA there is a lower proportion of South American patients in PPCS compared with RCPC.

Conclusions: In our department, no statistically significant differences have been observed regarding access to clinical studies. Thus, representativeness of all included groups is observed regardless of sex or nationality. Improving representativeness in clinical studies is essential to reduce health inequalities and to ensure that scientific findings benefit all affected groups equally.

REFERENCES: NIL.

Acknowledgments: NIL.

Disclosure of Interests: None declared.