SP0126 CLINICAL IMPORTANCE OF ANA ANTI-DSF70 ANTIBODIES
Authors: Johan Rönnelid
Journal: Annals of the Rheumatic Diseases (2019)

<h3>Background:</h3> Analysis of anti-nuclear antibodies (ANA) is a hallmark in the classification criteria for many systemic rheumatic diseases, including systemic lupus erythematosus (SLE). ANA investigations performed with indirect immune fluorescence (IF) on HEp-2 cells detect autoantibodies against a large number of nuclear autoantigens, and is often followed by, or done in parallel to, investigations which determine the autoantibody specificities causing the IF ANA staining. Two IF ANA-associated SLE-specific autoantibodies, anti-double stranded DNA and anti-Sm, are included both in previous as well as emerging SLE classification criteria. But IF ANA itself is also included in all of these classification criteria (1-3). This is because a positive IF-ANA is regarded as an independent risk factor for SLE, irrespective of what autoantibody specificity determines the nuclear staining. Antibodies against lens epithelium-derived growth factor 70/75 kD autoantigen creates a specific dense fine speckled IF-ANA pattern, and the autoantibodies are generally called anti-DFS70. The rather recently described anti-DFS70 pattern is unique and has obtained the AC-2 pattern in the recent universally accepted International Consensus on ANA Patterns (ICAP) classification system (www.anapatterns.com), but was not previously recognised and might be misinterpreted. In contrary to other IF-ANA patterns/specificities, isolated anti-DFS70 is not associated with systemic rheumatic diseases, and might even be more common among healthy individuals than among diseased populations (4). However, when anti-DFS70 occur together with other ANA specificities, different IF-ANA patterns may predominate. <h3>Objectives:</h3> The European Consensus Finding Study Group on autoantibodies (ECFSG), a.k.a. the EULAR autoantibody study group, regularly investigate autoantibody content in new autoantibody reference standards produced to obtain consistent results between clinical laboratories. <h3>Methods:</h3> In the 2018 ECFSG serum investigation, a newly produced pooled anti-DFS70 reference standard was investigated blindly concerning IF ANA patterns and autoantibody specificities by 38 participating laboratories. <h3>Results:</h3> Most laboratories correctly described the IF-ANA pattern correctly as the dense fine speckled AC-2 pattern; however 5/38 laboratories reported the pattern as homogenous (AC-1). Concerning autoantibody specificities, the standard was determined to be monospecific for anti-DFS70. This new reference standard has recently been described (5), and will be available via www.autoab.org. <h3>Conclusion:</h3> In my talk I will give a background on the emergence of anti-DFS70 antibodies, and report on the outcome of the ECFSG investigation of the anti-DFS70 reference standard. Moreover, I will present an algorithm for how to incorporate investigations for anti-DFS70 in ANA investigations in a cost efficient way. <h3>References:</h3> [1] E. M. Tan, et al. Arthritis Rheum. 25, 1271 (1982). [2] M. Petri, et al. Arthritis Rheum 64, 2677 (2012). [3] S. K. Tedeschi, et al. Ann Rheum Dis (2019). [4] M. Mahler, et al. J Rheumatol 39, 2104 (2012). [5] A. Dellavance, et al. Clin Chem Lab Med in press (2019). <h3>Disclosure of Interests:</h3> None declared