Background Positive antinuclear antibosies (ANA) may lead to additional testing and potentially even inappropriate treatment in patients with rheumatic symptoms not caused by systemic lupus erythematosus (SLE). The aim of our study was to evaluate if autoantibodies directed against DFS70 can be used to exclude SLE in ANA positive patients.
Patients and methods Anti-DFS70 antibodies were determined by chemoluminescence assay (CIA) in sera of 352 apparently healthy individuals (AHI), 300 patients with SLE, 335 patients with other connective tissue diseases (CTD) including 56 patients with undifferentiated connective tissue disease (UCTD), and 660 non-CTD patients (302 rheumatoid arthritis, 94 ANCA-associated vasculitis, 87 atopic rhinitis, 135 paediatric patients with celiac disease, and 42 autoimmune liver diseases). Furthermore, 1048 patients of a routine cohort with positive ANA results determined by immunofluorescence on HEp-2-cells showing positive staining of the chromatine region and negative result in confirmatory assays for antibodies against dsDNA, histone, nucleosome, and DNA-topoisomerase 1 antibodies were included in this study.
Results In AHI and in the non-CTD cohort, anti-DFS70 antibodies occur with a prevalence of 5.1% and 2%, respectively. Of the 1048 selected routine sera, 205 (19.6%) were positive for anti-DFS70 antibodies. Various diseases but no definite SLE were diagnosed according to available data of 116 of anti-DFS70 positive patients. Of the 300 SLE patients, only one patient was low titred positive for anti-DFS70 antibodies in addition to dsDNA, nucleosome, Ro/SS-A and La/SS-B autoantibodies. In the non-CTD group, only 6 of 579 patients (1.2%) were positive for anti-DFS70 antibodies, all of them also show disease specific autoantibodies. In patients with UCTD, 6 (10.7%) were anti-DFS70 antibody positive in the absence of disease specific autoantibodies. Up to now, no development of SLE was observed in these patients.
Conclusion If anti-DFS70 antibodies are positive in the absence of SLE specific autoantibodies, SLE can be excluded with high certainty.
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