POS0263 CLINICAL RELEVANCE OF DFS70 ANTIBODIES – A MULTICENTRE STUDY
Authors: A. S. Pinto, J. P. Vilas, F. Cunha Santos, M. Cunha, B. Samões, A. Eduarda Porto Raposo, P. Abreu, E. Costa, N. Madeira, J. F. Ferreira, C. Vaz
Journal: Annals of the Rheumatic Diseases (2021)

Background: Anti-Dense Fine Speckled 70 (DFS70), also known as lens epithelium-derived growth factor (LEDGF) is a common finding when ANA are positive (1.7% in the whole population and 4.6% in the ANA-positive samples). DFS70 antibodies are rare in SARD, especially in the absence of clinical evidence or concomitant anti-extractable nuclear antigen (ENA) antibodies. Objectives: Our study aimed to understand the meaning of anti-DFS70 antibodies and characterize the clinical and serological features of patients with anti-DFS70 positivity. Methods: We performed a retrospective observational study of consecutive patients followed up at 9 Portuguese Rheumatology Centres observed from January 2018 until April of 2020 with anti-DFS70 antibodies positivity. Descriptive statistics were presented as mean ± standard deviation if normally distributed or as median and interquartile range if non-normally distributed (continuous variables) or as absolute and relative frequencies (categorical variables). Sensibility and specificity were calculated. Positive and negative predictive values were calculated between patients with and without SARD-specific autoantibodies. Associations between DFS70 with other disease-specific antibody and clinical manifestations were tested using Chi-Square or Fischer’s Exact Test, as appropriate. Results: 120 patients were included, 99 (82.5%) were female with a mean age of 47.8 ± 18.2 years. 96.7% of the patients had ANA titters ≥1:160 (32.5% 1:160; 38.3% 1:320; 16.7% 1:640; 7.5% 1:1280 and 1.7% 1:2560) and 3.3% ANA &lt;1:160. The main clinical reasons for ANA determination was arthralgia (44.2%), arthritis (11.6%) and Raynaud Phenomenon (RP) (10%). The main analytical reason (7.5%) was an elevation of inflammatory parameters (C-Reactive Protein (CRP) or Erythrocyte Sedimentation Rate (ESR), leukopenia (3.3%) and anaemia (2.5%). Concerning the immunology: 58.3% of patients didn´t have an associated antibody, 9.2% had a positive rheumatoid factor, 5.8% positive ds-DNA, 4.2% histone and 3.3% SS-A. 26 patients had more than one associated antibody. 30 (25%) patients were healthy; 43 (35.8%) patients had Systemic Autoimmune Rheumatic Diseases (SARD) and 47 patients (39.2%) had other diseases (non-SARD). Among patients with a SARD, 16 patients presented an isolated positive anti-DFS70 and 27 patients had other antibodies associated. There was found a positive association with non-SARD and arthralgia (p=0.001) and SARD with arthritis (p&lt;0.001). There was an association with SARD and raised inflammatory parameters (p=0.045), but no association was found with anaemia (p=1.000) or leukopenia (p=0.131). Comparative analysis is described in Table 1, with chi-square or Fischer tests, as appropriated. The sensitivity of isolated DFS70 was 70.1% and specificity was 62.8%. The positive predictive value was 77.1% and the negative predictive value was 54.0%. Table 1. Comparative analysis using chi-square or Fischer test SARD Non-SARD p-value Arthralgia, n 10 43 0.001 Arthritis, n 14 0 &lt;0.001 Raynaud Phenomenon, n 7 5 0.114 Raised Inflammation parameters, n 6 3 0.045 Anaemia, n 1 2 1.000 Leukopenia, n 3 1 0.131 Conclusion: We concluded that 64.2% of patients with positive DFS70 did not present a SARD and if we only consider patients with isolated anti-DFS70, 77.1% didn´t present a SARD. Therefore, in our study, 22.9% of the patients presented a SARD, which was associated with some clinical features like arthritis or raised inflammatory parameters (p&lt;0.05). Although isolated anti-DFS70 are not specific of a particular condition, our study supports that it can be used as a negative predictor of SARD, if a correlation with clinical and laboratory features is made. References: [1]Leuchten, N. et al. Performance of Antinuclear Antibodies for Classifying Systemic Lupus Erythematosus: A systematic literature review and meta-regression of diagnostic data. Arthritis Care Res. 70, 428–438 (2018). [2]Carter JB, Carter S, Saschenbrecker S, Goeckeritz BE (2018) Recognition and relevance of anti-DFS70 autoantibodies in routine antinuclear autoantibodies testing at a community hospital. Disclosure of Interests: None declared