B-080 Clinical Utility of the Detection Anti-DFS70 Autoantibodies by a Novel Fully Automated Multiplexed Microarray Immunoassay for the Assessment of Autoimmune Connective Tissue Diseases

Abstract Background Detection of autoantibodies directed to Dense Fine Speckled 70 (DFS70), also known as lens epithelium-derived growth factor (LEDGF) helps to confirm the DFS pattern observed in the indirect immunofluorescence assay on HEp-2 cells (HEp-2 IFA). Though its clinical relevance is still a matter of debate, anti-DFS70 autoantibodies have been reported to have a negative association with autoimmune connective tissue diseases (CTD), in the absence of autoantibodies to other common extractable nuclear antigens (ENA). We evaluated the clinical utility of this marker, in the presence and in the absence of other autoantibodies associated with CTD, based on the 15-autoantibody profile performed by a novel, single-use, multiplexed microarray immunoassay, for the simultaneous the detection of IgG autoantibodies directed to dsDNA, SS-A 60, TRIM21 (SS-A 52), SS-B, Sm, Sm/RNP, U1RNP, Jo-1, Scl-70, Centromere B, Chromatin, Ribosomal P, DFS70, RNAP III and CCP2. Methods Banked, de-identified serum samples from 667 patients diagnosed with ANA-associated CTD in accordance with current guidelines 171 patients with systemic lupus erythematosus (SLE), 135 with systemic sclerosis, 125 with Sjögren’s syndrome (SjS), 152 with mixed CTD (MCTD), and 84 with idiopathic inflammatory myopathies (IIM), 558 disease controls were tested using the MosaiQ AiPlex® CTDplus microarray assay (AliveDx, Switzerland). Prevalence of anti-DFS70 in the CTD, disease controls and blood donors’ groups was calculated. The frequency of anti-DFS70 plus or minus other autoantibodies in the different groups was determined, as was the performance of this marker in the discrimination of CTD. Results Anti-DFS70 antibodies were detected in 11/233 (4.72%) samples from blood donors, in 28/558 (5.01%) disease controls, and in 19/667 (2.84%) samples from patients diagnosed with CTD SLE: 11/171 (6.43%), SSc: 4/135 (2.96%), SjS: 1/125 (0.8%), MCTD: 1/152 (0.65%), IIM: 2/84 (2.38%). Excluding equivocal and invalid results, 16 out of 19 (84.2%) samples in the CTD group and 0 out of 22 (0%) in the disease controls were reactive for anti-DFS70 and had 1 or more additional autoantibodies reactivities. 3 out of 19 (15.8%) samples in the CTD group and 22 out of 22 (100%) in the disease controls were reactive for anti-DFS70 and, at the same time, non-reactive for all other 14 autoantibodies. Sensitivity of anti-DFS70 in the discrimination of CTD and non-CTD (disease controls) was 84.2% (95% CI: 60.4%, 96.6%) and specificity was 100% (95% CI: 84.6, 100) (see Table for details). When analyzing blood donors separately or together with disease controls, specificity was 80.0% and 94.1%, respectively. Conclusion In the present retrospective cohort, anti-DFS70 auto-antibodies, in the absence of other common autoantibodies showed high specificity for the exclusion of CTD.