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Increased prevalence of ANA and Anti-SSA in African American rheumatoid arthritis patients is not associated with increased serum chemokine concentrations

Tyler J. Sevco, Douglas P. Landsittel, Chengli Shen, Larry W. Moreland

Background: African American (AA) rheumatoid arthritis (RA) patients have increased disease activity compared to Caucasian (CAU) RA patients. Serum chemokines, such as CXCL10, are increased in RA patients and may function as markers of disease activity. The aim of this study was to compare autoantibody seropositivity in AA and CAU RA patients and analyze the link between antibody positivity and serum chemokine concentration.

Methods and Findings: 93 AA RA patients and 93 CAU patients from the University of Pittsburgh cohort of RA patients were matched using a propensity model with race as the outcome and age, gender, body mass index (BMI), disease duration, anti-tumor necrosis factor (TNF) use, rheumatoid factor (RF) positivity, and cyclic citrullinated peptide (CCP) positivity as the predictor variables in a logistic regression. Plasma from the matched subjects was analyzed for autoantibodies including antinuclear antibody (ANA), anti-Sjogren's syndrome-related Antigen A (SSA), and anti-Sjogren's syndromerelated Antigen B (SSB). To evaluate differences in serum chemokine concentrations, anti-SSA positive samples were matched with anti-SSA negative samples for age, gender, disease duration, RF positivity, and CCP positivity using a propensity model. CXCL10 was measured using an ELISA assay. Anti-SSA was more prevalent in AA RA patients compared to CAU RA patients (11.70% vs. 3.23%; p=0.02). ANA was more prevalent in AA RA patients (21.28% vs. 10.75%; p=0.04). A total of 14 patients (7.57%) were anti-SSA positive. Anti-SSA positivity was not associated with increased serum CXCL10 levels compared to the anti-SSA negative group. RF positivity was associated with an increased serum CXCL10 concentration compared to the RF negative group (253.14 vs 153.46 pg/ml).

Conclusions: AA RA patients have an increased prevalence of anti-SSA and ANA compared to CAU RA patients, which may be contributing to the increased disease activity seen in this population via a mechanism outside of the CXCL10 chemokine pathway.