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Rates of end-organ disease in systemic lupus erythematosus (SLE) differed significantly among races and ethnicities in a longitudinal California cohort, researchers found.

The burden on white patients was the lightest overall, while individuals self-reporting as Asian or Hispanic showed the highest rates across four categories of organ damage, according to Alfredo Aguirre, MD, of the University of California San Francisco, and colleagues.

For example, , about 30% of white patients had developed renal disease 40 years after SLE diagnosis, compared with 50% of those identifying as Black, nearly 70% of Asian patients, and about 72% of Hispanic individuals.

The gaps between racial/ethnic groups were narrower for hematologic, neurologic, and cardiovascular disease, but the same pattern was evident. This was also the case for patients with multiorgan involvement (at least two organ systems with disease): less than 35% of white patients were affected by year 40, versus more than 60% of Asian and Hispanic participants in the so-called .

These results "serve a major goal of lupus research: to identify patients who are at risk for severe disease trajectories," Aguirre and colleagues wrote. The findings also reflect overall trends in lupus, in which nonwhite groups show and than do whites (the latter a previous finding from CLUES).

CLUES -- the California Lupus Surveillance Project -- is an ideal testbed for studies of lupus epidemiology by race/ethnicity because of the state's diverse population. SLE patients living in San Francisco in 2007-2009 were identified from clinic records and, beginning in 2014, invited to join CLUES. Participants met standard clinical criteria for SLE and allowed their records to be examined; some underwent follow-up exams with lab tests and specimen collection.

For the current analysis, Aguirre and colleagues pulled data on 326 CLUES members. About 90% were women. The race/ethnicity breakdown was 97 white, 76 Hispanic of any race, 35 non-Hispanic Black, and 118 non-Hispanic Asian.

Hispanic patients showed the greatest increase in risk for organ disease relative to white patients. Hazard ratios for the different organ categories in this comparison were as follows:

• Renal: 2.93, 95% CI 1.82-4.71

• Hematologic: 2.72, 95% CI 1.29-5.71

• Multiorgan: 3.28, 95% CI 1.83-5.89

The same calculation for Asian versus white patients yielded similar results. In no case did differences in risk for neurologic or cardiovascular disease reach statistical significance, but numerical trends pointed in the same direction.

As for reasons underlying the disproportions in end-organ disease, Aguirre and colleagues said they were "multifactorial and complex, and additional studies will be needed to investigate the contributions of social and biologic factors" involved. Other studies, the researchers pointed out, had suggested that access to healthcare, poverty, racial/ethnic discrimination, and treatment compliance may explain at least some of the discrepancies. But genetic differences may play a part too, the team cautioned.

Limitations to the analysis included that race/ethnicity was self-reported and that relatively few Black patients were enrolled. Also, because people who died after a lupus diagnosis prior to CLUES's launch obviously could not be enrolled, any racial/ethnic differences in mortality could bias the study's results. Another potential source of bias: differences in time from SLE onset to diagnosis.

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