Ethnic disparities among patients with systemic lupus erythematosus in South Carolina

Abstract

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

Methods: 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.

Results: 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.

Conclusion: 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.