SAT0275 PERFORMANCE OF THE ANTISYNTHETASE ANTIBODIES AND THEIR INDIRECT IMMUNOFLUORESCENCE PATTERNS IN THE ANTISYNTHETASE SYNDROME DIAGNOSIS

Background: The antisynthetase syndromes (ASSD) are characterized by the presence of anti-aminoacyl transfer RNA synthetase (ARS) autoantibodies; which difficult the binding of amino acids to the transfer RNA during the protein synthesis. ARS can be detected by indirect immunofluorescence (IIF), and can be identified by immunoblot assay and ELISA (Enzyme-Linked ImmunoSorbent Assay) and immunoblotting. The main clinical features of the ASSD are myositis, arthritis, interstitial lung disease, Raynaud’s phenomenon, mechanic hands, and fever. Two ASSD diagnosis criteria have been developed; those proposed by Connors, and the stricter criteria proposed by Solomon (1, 2). Objectives: To evaluate the performance of the ARS and their IIF patterns in the ASSD diagnosis. Methods: We performed an observational retrospective study in one center during the period 06/2008-06/2018. We searched all the myositis immunoblots (Euroimmun assay) requested by the Rheumatologists under suspicion of ASSD or myositis. We assessed: 1) the rate of cases with positive ARS; 2) the rate of cases with Connor’s or Solomon’s diagnosis criteria fulfillment; and 3) their relation with the IIF patterns (Hep-2 cells; ≥1/80) evaluated by an expert in autoimmune tests. Results: A total of 140 myositis immunoblots were searched. Twenty-seven cases (19.3%) presented positive ARS: anti-Jo1 (n=13), anti-PL-12 (n=7), anti-PL-7 (n=1), anti-EJ (n=2), and anti-OJ (n=4). Twenty-five of these (17.9%) fulfilled Connors’ criteria, and 15 (10.7%) additionally met Solomon’s criteria. Thus, the fulfillment of Connor’s and Solomon’s criteria in patients with a positive ARS was of 92.6% and 55.5%, respectively. All cases (100%) with positive ARS presented positive immunofluorescence: 19 (70.4%) showed a cytoplasmic pattern (10 of them with an associated nuclear pattern) and 8 cases (29.6%) presented only a nuclear pattern. On the other hand, 99 of the 113 cases (87.6%) with negative ARS presented positive IIF: 29 (25.7%) showed a cytoplasmic pattern (21 of them with an associated nuclear pattern) and 42 cases (37.2%) presented only a nuclear pattern. Correlating the ARS positivity, IIF pattern and the diagnosis criteria fulfillment: - 13 of 15 cases (86.6%) with positive ARS and Solomon’s criteria fulfillment presented a cytoplasmic pattern; and 2 of 15 cases (13.3%) presented only a nuclear pattern. - 13 of 19 cases (68.4%) with positive ARS and cytoplasmic pattern fulfilled Solomon’s criteria; and 6 only fulfilled those from Connors’. Conclusion: One-fifth of the immunoblots requested by Rheumatologists presented positive ARS; almost all these cases fulfilled Connor’s criteria, and more than a half fulfilled the stricter Solomon’s criteria. All patients with positive ARS, and a high rate of those without ARS, presented positive IIF. The presence of a cytoplasmic pattern was considerably higher in patients with ARS positivity and in those that met Solomon’s criteria. Thus, our results suggests that in patients evaluated by a Rheumatologist, with clinical suspicion of ASSD or myositis and with ARS positivity, the probability of fulfilling Solomon’s criteria is higher when the IIF presents a cytoplasmic pattern than when only a nuclear pattern is observed. Nevertheless, presenting only a nuclear pattern does not exclude the detection of ARS in the myositis immunoblot and the fulfillment of Solomon’s criteria. References [1] Solomon J, et al. Jornal brasileiro de pneumologia. 2011;37(1):100-9. [2] Connors GR, et al. Chest. 2010;138(6):1464-74. Disclosure of Interests: Martin Greco: None declared, Maria Jesus Garcia de Yebenes: None declared, Inmaculada Alarcon: None declared, Anahy Brandy-Garcia: None declared, Inigo Rua-Figueroa: None declared, Estibaliz Loza Grant/research support from: Roche, MSD, Pfizer, Abbvie, BMS, UCB, Actelion, Celgene, Grunenthal and Sanofi, Teresa Oton: None declared, Francisco Rubino: None declared, Juan Manuel Diaz: None declared, Felix Francisco: None declared, Soledad Ojeda: None declared, Loreto Carmona Grant/research support from: Abbvie, Actelion, Astellas, BMS, Eisay, Gebro Pharma, Grunenthal, Leo Pharma, Lilly, MSD, Novartis, Pfizer, Roche, Sanofi-Aventis and UCB Pharma, Paid instructor for: Novartis