Antibodies to phosphatidylserine-prothrombin complex and annexin v as risk factors for the development of thrombotic complications in patients with systemic lupus erythematosus

Background: 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. Objectives: To study the prevalence of aPS-PT and anti-annexin V antibodies and their role in the development of thrombotic complications. Methods: 79 SLE patients were enrolled in the study (M/F 7/72; mean age 11.0 years, range. 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. Results: 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 (>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<0.05); there were no significant differences between the main group and the comparison group (p>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<0.001), anti-annexin V antibodies IgM and IgG (r=0,72 and r=0,47, p<0,001). In a subgroup with elevated aPS-PT levels (>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). Conclusions: 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 (>16 U/ml) increase the incidence of thrombotic complications in patients with SLE. Disclosure of Interest: None declared DOI: 10.1136/annrheumdis-2018-eular.4757 Citation: Ann Rheum Dis, volume 77, supplement Suppl, year 2018, page A392Session: SLE, Sjögren’s and APS – clinical aspects (other than treatment)