Autoantibodies to dense-fine-speckled 70 (DFS70) do not necessarily rule out connective tissue diseases

Abstract

Objectives: In some patients with antinuclear antibodies (ANA), a pattern called anti-dense-fine-speckled-70 antibody (anti-DFS70) can be detected. Presence of anti-DFS70 is less frequently observed in patients with connective tissue diseases (CTD) and is therefore used as an exclusion criterion by some rheumatologists. To date, however, it is unclear as to what extent the presence of an anti-DFS70 can reliably rule out CTDs.

Methods: Data of 460 patients who were tested for the presence of anti-DFS70 at University Hospital Bonn, Germany, were analyzed. Patients were examined with regard to clinical symptoms and signs, type of disease, type of CTD, fulfillment of the classification criteria, presence of anti-DFS70, other systemic autoantibodies and ANA titers by indirect immunofluorescence (IIF) assays and line immunoassays. Differences in DFS70 antibody status between patients with CTD were examined. In addition, specificity, sensitivity, and positive predictive values for different ANA titers were calculated.

Results: In 182 of the 460 patients (of whom 79.8% were female), CTD was diagnosed. 354 patients (77.0%) tested negative, 81 (17.6%) positive and 25 (5.4%) borderline for anti-DFS70. Twenty-one patients (25.9%) with a positive result had CTD. No significant differences were observed between anti-DFS70 positive and anti-DFS70 negative patients with CTD concerning age, gender, symptoms, clinical signs, and other disease-specific antibodies. However, of these 21 patients, only one patient showed the monospecific appearance of anti-DFS70. Anti-DFS70 had a sensitivity and a specificity of 26.9% and 86.8%, respectively, with a positive predictive value of 68.2% at an ANA titer of ≥1:160 with respect to the absence of CTD.

Conclusions: Autoantibodies to DFS70 seem to be prevalent in CTD patients and are thus not a good exclusion criterion. The monospecific occurrence of anti-DFS70 can, however, be helpful in ambiguous situations.

Keywords: Antinuclear antibodies; Connective tissue disease Systemic lupus erythematosus; Dense-fine-speckled 70; Mixed connective tissue diseases; Primary Sjögren's syndrome.