Background The presence of anti-nuclear antibodies (ANA) has been considered a characteristic of systemic autoimmune diseases (SAD). Patients are frequently referred for study because they have ANA and are followed because of the possibility to develop SAD. Approximately, 20% of healthy individuals with ANA detected by indirect immunofluorescence (IFI), especially at low titers, have a dense, fine speckled pattern (DFS) that frequently corresponds to the presence of anti-DFS70 antibodies. The importance of this antibody is due to its low prevalence in subjects with ASD (<1%) compared to its presence in 33.1% of healthy subjects with ANA.

Objectives To describe the usefulness of Anti-DFS70 in a series of patients presenting ANA.

Methods We collected prospectively throughout the year 2016 all the patients referred to a tertiary hospital for ANA study and in whom the presence of anti-DFS70 antibodies was confirmed. All patients underwent a thorough medical history, physical examination, and relevant follow-up tests were performed according to the clinical presentation. The IFI was performed in a Menarini Zenit-Up/GSight system, as well as ANA screening in Hep-2000 (Fluorescent IgG ANA-Ro Test System-immunoconcepts) and the detection of anti-DFS70 antibodies by immunoblot (ANA + DFS70 Dot Blot-Alphadia).

Results We collected in a period of 12 months a total of 7 patients with anti-DFS70 antibodies. Most of them (6/7) were referred because of non-specific symptoms such as arthralgia, fatigue, thrush, edema, ... and the presence of ANA. The findings are detailed in Table 1.

Conclusions Anti-DFS70 is a valuable biomarker, with a very low prevalence in SAD, which gives it a role as a negative predictive marker of developing SAD when it is appears alone. Its detection in serum with a dense fine speckled pattern ANA (IFI) should be part of the protocol of the immunology laboratory. It is a cost-effective determination, as demonstrated in a recent study, by avoiding the costs associated with the follow-up of these patients. In our case, its finding allowed us to reassure the patient and avoid the accomplishment of further complementary tests, as well as an unnecessary monitoring.

Disclosure of Interest None declared