Racial and Ethnic Differences in the Prevalence and Time to Onset of Manifestations of Systemic Lupus Erythematosus: The California Lupus Surveillance Project

Abstract

Objective: The California Lupus Surveillance Project (CLSP) is a population-based registry of individuals with systemic lupus erythematosus (SLE) residing in San Francisco County, California from 2007 to 2009, with a special focus on Asian/Pacific Islander and Hispanic patients. We used retrospective CLSP data to analyze racial and ethnic differences in lupus manifestations and in the timing and risk of developing severe manifestations.

Methods: A total of 724 patients with SLE were retrospectively identified. Prevalence ratios (PRs) of SLE manifestations were calculated using Poisson regression models stratified by race/ethnicity and adjusted for sex, age at SLE diagnosis, and disease duration. We studied onset of severe SLE manifestations after SLE diagnosis using Kaplan-Meier methods to examine time-to-event and Cox proportional hazards regression models to estimate hazard ratios (HRs). White patients were the referent group in all analyses.

Results: African Americans, Asian/Pacific Islanders, and Hispanic patients had increased prevalence of renal manifestations (PR 1.74 [95% confidence interval (95% CI) 1.40-2.16], PR 1.68 [95% CI 1.38-2.05], and PR 1.35 [95% CI 1.05-1.74], respectively). Furthermore, African Americans had increased prevalence of neurologic manifestations (PR 1.49 [95% CI 1.12-1.98]), and both African Americans (PR 1.09 [95% CI 1.04-1.15]) and Asian/Pacific Islanders (PR 1.07 [95% CI 1.01-1.13]) had increased prevalence of hematologic manifestations. African Americans, Asian/Pacific Islanders, and Hispanic patients, respectively, had higher risk of developing lupus nephritis (HR 2.4 [95% CI 1.6-3.8], HR 4.3 [95% CI 2.9-6.4], and HR 2.3 [95% CI 1.4-3.8]) and thrombocytopenia (HR 2.3 [95% CI 1.1-4.4], HR 2.3 [95% CI 1.3-4.2], and HR 2.2 [95% CI 1.1-4.7]). Asian/Pacific Islander and Hispanic patients had higher risk of developing antiphospholipid syndrome (HR 2.5 [95% CI 1.4-4.4] and HR 2.6 [95% CI 1.3-5.1], respectively).

Conclusion: This is the first epidemiologic study comparing lupus manifestations among 4 major racial and ethnic groups. We found substantial differences in the prevalence of several clinical SLE manifestations among racial/ethnic groups and discovered that African Americans, Asian/Pacific Islanders, and Hispanic patients are at increased risk of developing several severe manifestations following a diagnosis of SLE.

Figure 1.

Time to incident severe SLE manifestation following SLE diagnosis, stratified by race/ethnicity, among prevalent SLE cases in San Francisco County, 2007 – 2009