POS0712 “EXTRA”- CRITERIA ANTIPHOSPHOLIPID ANTIBODIES IN PATIENTS WITH ANTIPHOSPHOLIPID SYNDROME AND SYSTEMIC LUPUS ERYTHEMATOSUS (PRELIMINARY DATA)
Authors: F. Cheldieva, T. Reshetnyak, M. Cherkasova, N. Seredavkina, A. Lila
Journal: Annals of the Rheumatic Diseases (2021)

Background: The study of antiphospholipid antibodies (aPL), not included in the Sydney diagnostic criteria, in antiphospholipid syndrome (APS) and systemic lupus erythematosus (SLE) is poorly understood. Objectives: To determine the frequency of detection of IgA-aCL and IgA-aβ2GP1 and IgG antibodies to β2GP1 domain 1 (IgG-aβ2GP1-D1) in patients with APS with and without SLE. Methods: ELISA and chemiluminescence assays (CMA) were used to test 63 sera of patients: 22 (35%) with primary APS (pAPS) and 41 (65%) patients with APS and with SLE (secondary APS (sAPS)), with mean age 38,0 [33,0 – 43,0] years and disease duration 4,0 [0,1 – 9,9]. Both methods were used to test of IgG/IgM-aCL and IgG/IgM-aβ2GP1. CMA was used for research IgG/IgM/IgA-aCL, IgG/IgM/IgA-aβ2GPI and IgG-aβ2GP1-D1. Of them 49 (78%) (18 – with pAPS; 31 – with sAPS) displayed major thrombotic events and 18 of 22 pregnant women had pregnancy morbidity in past history. Lupus anticoagulant (LA) positivity was in 9 out of 12 patients who had it determined. LA was not investigated due to anticoagulant therapy in the remaining 52 patients. Results: IgG/IgM-aCL and IgG/IgM-aß2GP1 were recorded in 44/18 and 50/17 patients by ELISA and in 55/19 and 59/16 by CMA, respectively. IgA-aCL positivity was found in 35 (56%) of 63 patients. Thirty IgA-positive patients were positive for IgG-aCL by ELISA: 22 – IgG-aCL – highly positive, 6 – medium positive and 2 – low positive patients. IgM-aCL by ELISA was detected in 13 (37%) of 35 IgA-aCL positive patients: 11 – highly positive, 1 – medium positive and 1 – low positive. IgA-aCL was combined with IgG-aCL in 34 patients and with IgM-aCL in 16 patients in the CMA. IgG-aß2GP1 in ELISA was detected in 32 patients with IgA-aCL (24 –highly positive, 5 – medium positive and 3 – low positive) and in 34 – in CMA. IgM-aß2GP1 was combined with IgA-aß2GP1 with the same frequency in both methods (in 13 patients). IgA-aß2GP1 was detected in 30 (48%) of 63 patients. They were combined with both IgG-aCL and IgG-aß2GP1 in all cases in both methods. IgM-aCL and IgM-aß2GP1 were detected in 14 and 11 of 30 patients with IgA-aß2GP1, respectively. The combination of IgA-aß2GP1 with IgG-aCL by ELISA was in 27 (in most cases highly positive – 20) and with IgM-aCL – in 10 (highly positive - 8). IgG-aß2GP1 was detected in 28 patients with IgA-aß2GP1 (high positive – 21) and in 11 patients with IgM-aß2GP1 (high positive –7). IgG-aß2GP1-D1 was revealed in 48 (76%) patients. It was combined with IgG-aCL – in 38, with IgM-aCL – in 15 patients by the ELISA. The combination of IgG-aß2GP1-D1 by CMA was as follows: with IgG-aCL – in 46, with IgM-aCL – in 17, and with IgA-aCL – in 33 patients. In most cases, IgG-aß2gp1-D1 was combined with highly positive aCL levels. IgG-aß2GP1-D1 positivity was associated with IgG-aß2GP1 positivity in 42 – by ELISA and 47 – by CMA, IgМ-aβ2GP1 – in 13 and 14 patients by ELISA and CMA, respectively, and IgA-aß2GP1 – in 29. Isolated IgG-aß2GP1-D1 positivity was not observed. Conclusion: The frequency of IgA-aCL detection was 56% (35 patients out of 63), IgA-aβ2GP1 – 48% (30 patients out of 63), IgG-aβ2GP1-D1 – 76% (48 patients out of 63). There was not isolated positivity of this “extra” criterial antibodies. The presence of IgA-aCL, IgA-aβ2GP1, IgG-aβ2GP1-D1 was associated with highly positivity of IgG/IgM-aCL and IgG/IgM- aβ2GP1. Disclosure of Interests: None declared