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

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.