Antifibrillarin antibodies are associated with native North American ethnicity and poorer survival in systemic sclerosis

Objective. To examine the clinical correlates and survival in patients with antifibrillarin antibodies (AFA) in a large international study population consisting of well-characterized systemic sclerosis (SSc) cohorts from Canada, Australia, and the United States. Methods. Baseline clinical data from the prospective cohorts (Canadian Scleroderma Research Group, the Australian Scleroderma Cohort Study, and the American Genetics versus Environment in Scleroderma Outcome Study) were investigated. Clinical variables were harmonized and sera were tested for AFA using a commercially available SSc profile line immunoassay, regardless of the immunofluorescence staining pattern. Association of demographic and clinical features with AFA was investigated by logistic or linear regression. Further, a survival analysis was performed by Cox regression analysis. Results. A total of 1506 patients with SSc with complete serological profiles were included in the study. Fifty-two patients (3.5%) had antibodies detected against fibrillarin. Patients of African descent and Native North American ethnicity were more likely to be AFA-positive compared with other ethnicities. After adjustment for demographic factors, diffuse involvement, and intestinal bacterial overgrowth requiring antibiotics, gastrointestinal reflux disease showed a trend for association with AFA. Further, AFA positivity was associated with shorter survival independently of demographic factors and disease type (HR 1.76, 95% CI 1.11-2.79, p = 0.016). Conclusion. In this large multinational SSc cohort, AFA was associated with Native American ethnicity and was an independent predictor of mortality.