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: A retrospective study was conducted on 324 patients who met well-established criteria for SLE and were followed between 2010 and 2024 at Hospital Fundación Jiménez Díaz in Madrid, Spain. Patients of ethnically Spanish origin were classified as Caucasian, while those identified as Latin American (including individuals from South and Central America, and Brazil), Asian, or of African descent were grouped as non-Caucasian. 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. Statistical methods included chi-square, t-test, Mann-Whitney U test, and multivariate logistic regression. Results: Of the cohort, 42.3% (n = 137) were non-Caucasian, 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 Caucasian patients (13.9%) compared to non-Caucasian patients (6.6%) (p = 0.04). In contrast, anti-Sm antibodies were more commonly detected in non-Caucasian patients (26.3% vs. 16.6%; p = 0.03). Non-Caucasian 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 Caucasian patients. Current prednisone use was also more frequent among non-Caucasian patients (41.3% vs. 24.7%), while the use of immunosuppressants was similar between the two groups. Conclusion: Within a universal, publicly funded healthcare system, ethnic differences did not translate into marked disparities in clinical manifestations of SLE. However, the higher disease activity and greater glucocorticoid use observed in non-Caucasian patients may reflect inherent variations in disease expression rather than inequities in care delivery.