Background Systemic Lupus Erythematous (SLE) is a chronic multi-systemic autoimmune disease. Despite therapeutic advancements, lupus nephritis (LN), which occurs in 25%–75% of individuals with SLE, remains a major cause of mortality. Prior studies have demonstrated poor outcomes in SLE occurring more frequently in both ethnic minority groups as well as in those with low socioeconomic status (SES). Factors attributing to greater mortality rates in these populations include patient resistance to treatment, compliance, low SES and genetics.
Methods Subjects were selected from SCOLR, a prospective registry enrolling all-comers with SLE. Inclusion criteria were LN subjects with available biopsy report. Subjects with renal transplant and unknown LN class were excluded. Data collected included demographics, insurance information, clinical and serologic variables specifically to establish an SLE disease activity index (SLEDAI). Subjects were categorized by self-reported ethnicity: White Hispanic, White non-Hispanic, Black, and Asian/Pacific Islander. Further sub-analysis was carried out on individuals with public vs. private insurance. Insurance and ethnicity were used as surrogates for socioeconomic status and descriptive statistical analyses were calculated to determine if observed differences were statistically significant.
Results One hundred and sixty-two medical charts were reviewed. Of those, 50% of subjects were White Hispanic, 31.8% White non-Hispanic, 8.7% Black, and 6.6% Asian/Pacific Islander. After adjusting for age, sex, and BMI, public insurance was independently associated with the prevalence of LN (p=0.038).
We performed a subgroup analysis of the 35 LN subjects to observe the association between SES with treatment outcomes. Proteinuria was higher in subjects with public insurance at baseline and this difference was statistically significant (p=0.053) with a similar trend at 6 months. Baseline and 6 month SLEDAI means were higher in subjects with public compared to private insurance.
Baseline, 6 and 12 month SLEDAI means were significantly lower in Asian/PI compared to other ethnic groups. While White non-Hispanics demonstrated SLEDAI improvement over 6 months, the majority of Asians/PI, Blacks, and Hispanics demonstrated no change or worsened disease activity.
Conclusions Low socioeconomic status, as determined by the proxy variables of ethnicity and insurance type, is associated with greater mortality in SLE. To our knowledge, this is the first study that compares differences in treatment response in LN patients with low-SES in southern California. Our findings, which confirm the association of SES with long-term outcomes in SLE and LN, are in line with previous studies. More studies with greater power are warranted to validate these findings and improve healthcare outcomes.
Funding Source(s): None
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