THU0349 Antibodies to phosphatidylserine-prothrombin complex and annexin v as risk factors for the development of thrombotic complications in patients with systemic lupus erythematosus
Authors: E. Belolipetskaia, I. Beliaeva, V. Mazurov, S. Lapin, O. Tkachenko, V. Guseva, O. Inamova
Journal: Annals of the Rheumatic Diseases (2018)

<h3>Background</h3> Seronegative antiphospholipid syndrome (APS) is a type of APS where the diagnostic levels of "classical" antiphospholipid antibodies (aPL) are not detected, though antibodies to the phosphatidylserine-prothrombin complex (aPS-PT) and anti-annexin V antibodies can be present. The role of these antibodies in the diagnosis of APS needs to be clarified. <h3>Objectives</h3> To study the prevalence of aPS-PT and anti-annexin V antibodies and their role in the development of thrombotic complications. <h3>Methods</h3> 79 SLE patients were enrolled in the study<b> (</b>M/F 7/72; mean age 11.0 years, range.<sup><sup>18,0;78,0</sup></sup> The main group consisted of 38 SLE patients with thrombotic complications and/or obstetric complications (mentioned in the classificational criteria for APS), a comparison group consisted of 41 SLE patients without thrombotic/obstetric complications. The groups were comparable in age, duration and SLE activity. ELISA was used to test for aPL: anticardiolipin (aCL) IgG and IgM, anti-β2-glycoprotein-1 antibodies IgGAM (anti- β2GPI), antibodies to phosphatidylserine-prothrombin complex (anti-PS/PT) IgG/M, anti-annexin V antibodies IgG/IgM. Lupus anticoagulant (LA) was evaluated using the DRVV test method. <h3>Results</h3> In 11 patients (29%) of the main group "classical" aPL were not detected, although one SLE patient with thrombosis had elevated levels of antibodies to annexin V IgG (&gt;5 U/ml). Sensitivity and specificity of aPL for the diagnosis of APS in patients with SLE were 19% and 96% for anti-PS/PT, 11% and 94% for anti-annexin V antibodies IgG, 11% and 88% for anti-annexin V antibodies IgM respectively. When comparing two groups using rank test, significant differences were revealed for aCL IgG, anti- β2GPI IgGAM levels(p&lt;0.05); there were no significant differences between the main group and the comparison group (p&gt;0.05) for levels of aCL IgM, aPS-PT and anti-annexin V antibodies. A positive correlation was revealed between the level of aPS-PT and the following aPL: LA (r=0.45, p=0.00006), aCL IgM and IgG (r=0.4 and r=0.45, p&lt;0.001), anti-annexin V antibodies IgM and IgG (r=0,72 and r=0,47, p&lt;0,001). In a subgroup with elevated aPS-PT levels (&gt;16 U/ml, 6 patients) thrombotic complications, venous thrombosis and its recurrence developed significantly more often than in a subgroup with a normal aPS-PT levels (OR=3.4, p=0.02, OR=4.1, p=0.02, OR=1.5, p=0.01, respectively). <h3>Conclusions</h3> 1. Anti-annexin V antibodies IgG and IgM have high specificity (94% and 88% respectively), but low sensitivity (11% and 11% respectively) for diagnosis of APS in SLE patients.2. A level of aPS-PT has a positive correlation with both "classical" aPL and anti-annexin V antibodies, and has a sensitivity of 19% and a specificity of 96% for the diagnosis of APS in SLE patients. 3. Elevated levels of aPS-PT (&gt;16 U/ml) increase the incidence of thrombotic complications in patients with SLE. <h3>Disclosure of Interest</h3> None declared