[Clinical significance of determination of DFS70 antibodies to rule out connective tissue diseases]. / Klinische Wertigkeit der Bestimmung von DFS70-Antikörpern für den Ausschluss von Kollagenosen.

BACKGROUND: Connective tissue diseases (CTD) are autoimmune diseases highly associated with the presence of antinuclear antibodies (ANA). Since ANA and musculoskeletal symptoms are not uncommon in the general population, differential diagnostic challenges frequently occur for the treating physician. Dense fine speckled antibodies (DFS70) were recently discovered but their presence appeared to be rare in CTD. METHODS: In this cross-sectional study a total of 270 patients treated in the Rheumatism Center of the Ruhr Area (Rheumazentrum Ruhrgebiet) were preferentially included, when they were ANA+ (≥1:80). Other autoantibodies and DFS70 antibodies were also investigated. The diagnosis of CTD was confirmed by rheumatologists. The sensitivity, specificity and the positive predictive value of DFS70 antibodies were differentially evaluated for various ANA titers. RESULTS: In 91 (33.7%) of the ANA+ patients (33.7%) the diagnosis of CTD was confirmed and in 84 (92.3%) the ANA titer was ≥1:160. The DFS70 antibodies were detected in 17 out of 130 ANA+ patients without CTD (13.1%) versus 2 ANA+ patients (2.2%) with CTD (p = 0.027). None of the patients with ANA 1:80 had DFS70 antibodies. The specificity of DFS70 antibodies to detect the absence of CTD was 97.6%, the sensitivity was 13.1% and the positive predictive value was 89.5%. There was almost no effect of the strength of the different ANA titers. CONCLUSION: It was found that DFS70 antibodies are rarely present in ANA+ patients with CTD but the diagnosis of CTD cannot be reliably ruled out solely by the presence of DFS70 antibodies; however, the high specificity of DFS70 antibodies can be of clinical importance in unclear situations and in cases of anxious patients.