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 SLE residing in San Francisco County, California from 2007–2009, with a special focus on Asians/Pacific Islanders (API) and Hispanics. We used retrospective CLSP data to analyze racial/ethnic differences in lupus manifestations and in the timing and risk of developing severe manifestations. Methods 724 patients with SLE were retrospectively identified. Prevalence ratios (PR) 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 regressions to estimate hazard ratios (HR). Whites were the referent group in all analyses. Results Blacks, APIs, and Hispanics had increased prevalence of renal manifestations [PR 1.74 (95%CI: 1.40–2.16), PR 1.68 (95%CI: 1.38–2.05), PR 1.35 (95%CI: 1.05–1.74)], respectively. Furthermore, Blacks had increased prevalence of neurologic manifestations [PR 1.49 (95%CI: 1.12–1.98)] and both Blacks [PR 1.09 (95%CI: 1.04–1.15)] and APIs [PR 1.07 (95%CI: 1.01–1.13)] had increased prevalence of hematologic manifestations. Blacks, APIs, and Hispanics, 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), 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), HR 2.2 (95%CI: 1.1–4.7)]. APIs and Hispanics had higher risk of developing antiphospholipid syndrome [HR 2.5 (95%CI: 1.4–4.4), HR 2.6 (95%CI: 1.3–5.1), respectively]. Conclusions This is the first epidemiologic study comparing lupus manifestations among four major racial/ethnic groups. We found 1) substantial differences in the prevalence of several clinical SLE manifestations among racial/ethnic groups, and 2) that Blacks, APIs, and Hispanics are at increased risk of developing several severe manifestations following SLE diagnosis.