AB1154 CLINICAL SIGNIFICANCE OF MONOSPECIFIC ANTI-DFS70 IN ANTINUCLEOLAR ANTIBODY (ANA)-POSITIVE PATIENTS

Background The most commonly used method for ANA detection is the indirect immunofluorescence test (IFI) on HEp-2 cells. Among ANA, anti-dense fine speckled (DFS) 70 antibodies produce a pattern (nuclear dense fine speckled) that can be confused with homogeneus or fine speckled pattern (typical of ANA-associated rheumatic disease, AARD). The presence of anti-DFS70 have been reported in a variety of clinical conditions. Isolated anti-DFS70 could be used as a differential marker for AARD. Objectives To analyse the clinical significance of isolated anti-DFS70 antibodies. Methods All the serum samples obtained in our hospital between January 2017 to December 2018 that were positive for ANA testing and negative for anti-extractable nuclear antigen (ENA) antibodies panel, were tested for anti-DFS70 (HEp-2/DFS70 knock-out IFA, A.MENARINI diagnostics). Demographic and clinical data were collected from anti-DFS70 positive adult patients. Results From 145 samples tested 68 were found positive for monoespecific anti-DFS70: 82.4% were women and the median age was 55.4±14.4 years. The ANA titer was greater than 1/320 in all of cases and 26.5% of patients had two positive determinations DFS70 separated 15.4±9.2 months. The reasons for requesting ANA were diverse (arthralgias in 33.8% of the cases), and most of them were ordered from primary care. Clinical follow-up was performed in 66.1% of the patients for a mean of 2.9 years (between 2 months and 7 years). Only 3 patients (4.1%) had a defined AARD: 2 systemic lupus erythematosus and 1 antiphospholipid syndrome, diagnosed years before. There were 5 patients with rheumatoid arthritis (7.3%) and one had sarcoidosis. Nineteen patients (27.9%) had an organ-specific autoimmune disease: 14 autoimmune hypothyroidism, 2 autoimmune hepatitis, 2 primary biliary cholangitis and 1 immune thrombocytopenia. Six patients (8.8%) were followed up because of undifferentiated connective tissue disease (they did not meet criteria for AARD). Other clinical associations found were obesity (13.2%), depression (8.8%), sleep disorders (8.8%), fibromyalgia 5,8%, cancer, asthma and psoriasis (2.9% each one of them). Thirty-nine patients (57.3%) did not have any autoimmune disease (systemic or localized). Conclusion In our experience, patients with monospecific anti-DFS70 ANA rarely present AARD, even though 42.7% of subjects showed autoimmune features. Rheumatoid arthritis patients occasionally had an isolated anti-DFS70 ANA. Therefore isolated anti-DFS70 may be potentially considered as marker of benign autoimmunity. References [1] Michael Mahler, Luis E. Andrade, Carlos A. Casiano, Kishore Malyavantham & Marvin J. Fritzler (2019): Anti-DFS70 antibodies: an update on our current understanding and their clinical usefulness, Expert Review of Clinical Immunology, DOI: 10.1080/1744666X.2019.1562903. [2] Bonroy C, Schouwers S, Berth M, Stubbe M, Piette Y, Hoffman I, et al.: The importance of detecting anti-DFS70 in routine clinical practice: comparison of different care settings. Clin Chem Lab Med 2018; 56:1090-9. [3] Shovman O, Gilburd B, Chayat C, Amital H, Langevitz P, Watad A, et al.: Prevalence of anti- DFS70 antibodies in patients with and without systemic autoimmune rheumatic diseases. Clin Exp Rheumatol 2017; 36:121-6. Disclosure of Interests None declared