Ethnic differences in disease activity among patients with systemic lupus erythematosus in a universal public healthcare system

Objective To evaluate ethnic disparities among patients with systemic lupus erythematosus (SLE) managed within a universal, publicly funded healthcare system. Methods Cross-sectional study based on a retrospective review of medical records of patients with SLE who attended the rheumatology outpatient clinics of the Hospital Fundación Jiménez Díaz (Madrid, Spain) between 2023 and 2024. Eligible patients were those who had been followed in the unit at any time between 2010 and 2024 and who met well-established criteria for SLE. Patients of ethnically Spanish origin were classified as Spaniards, while those identified as Latin American (including individuals from South and Central America, and Brazil), Asian, or of African descent were grouped as non-Spaniards. Disease activity was assessed using the SLEDAI and SLEDAS scores, as well as the DORIS remission criteria. Comparative analyses included clinical features, disease activity, and treatment. Group comparisons were performed using the Mann-Whitney U test, Student's t-test, chi-squared test, or Fisher’s exact test, as appropriate. Results Of the cohort of 324 SLE patients, 42.3% ( n = 137) were non-Spaniards, primarily Latin American (88.3%), followed by Asian (10.2%) and individuals of African descent (1.5%). No significant differences were observed in clinical manifestations or lupus nephritis histology. However, antiphospholipid syndrome was more frequent among Spaniard patients (13.9%) compared to non-Spaniard patients (6.6%) ( p = 0.04). In contrast, anti-Sm antibodies were more commonly detected in non-Spaniards (26.3% vs 16.6%; p = 0.03). Non-Spaniard patients exhibited greater disease activity, with higher mean SLEDAI-2K scores (mean ± standard deviation: 1.80 ± 2.65 vs 1.26 ± 1.84; p = 0.03) and SLE-DAS scores (2.06 ± 3.26 vs 1.34 ± 1.89; p = 0.01), as well as significantly lower DORIS remission rates ( p = 0.03) compared to Spaniard patients. Current prednisone use was 41.3% among non-Spaniard patients versus 24.7% in Spaniards. The use of immunosuppressants was similar between the two groups. Conclusion In a universal public healthcare system, we did not observe major ethnic disparities in clinical manifestations of SLE. Nonetheless, non-Spaniard patients showed higher disease activity, lower remission rates, and greater glucocorticoid use, suggesting differences in disease expression rather than inequities in care.