Racial/Ethnic Differences in Prevalence of and Time to Onset of SLE Manifestations: The California Lupus Surveillance Project (CLSP)

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.