Ethnic disparities among patients with systemic lupus erythematosus in South Carolina

To evaluate whether ethnic disparities in mortality exist among hospitalized patients with systemic lupus erythematosus (SLE) in South Carolina, USA.

Administrative data were obtained on all SLE patients (ICD-9 code 710.0) hospitalized in South Carolina between 1996 and 2003. An SLE-specific comorbidity index validated as a predictor of hospital mortality was used as a measure of overall comorbidity. Cox proportional hazards models were used to compare mortality rates between Caucasians and African Americans. Post-hoc analyses focused on determining whether disparities were present across different risk strata.

Of 6521 hospitalized patients with SLE (5728 female, 793 male), 1280 (19.6%) died. Annual mortality rates were 21.9% among Caucasians and 25.0% among African Americans. The comorbidity index score was significantly higher among African Americans [median 2.0 (interquartile range 0.0-4.0)] versus Caucasians [median 0.0 (IQR 0.0-3.0); p < 0.0001, Wilcoxon rank-sum test]; however, even after multivariate adjustment, African Americans had a 15% increased mortality risk (hazard ratio 1.15, 95% CI 1.02-1.29, p = 0.013). The disparity was strongest among those with less comorbidity (HR 1.39, 95% CI 1.05-1.81, p = 0.017). Among patients with low comorbidity index scores (n = 3485), the annual mortality rate was 8.1% among Caucasians and 9.7% among African Americans. No ethnic differences in mortality were seen for patients with higher comorbidity.

In South Carolina, ethnic disparities in SLE mortality exist, predominantly among those with the least illness severity. Studies are planned to help clarify whether access and quality of care play a role.