Antiphospholipid syndrome (APS) is an autoimmune disease characterized by thromboembolic events or pregnancy complications associated with circulating antiphospholipid antibodies (aPL-Abs). APS diagnosis needs the presence of both clinical and serological criteria (SAPORRO criteria, updated with Sydney criteria in 2006). However, no correlation between laboratory assays and the clinical thrombosis risk in patients with aPL-Abs was observed as only few patients with aPL-Abs developed clinical manifestations. Thrombin generation assays (TGA) is a global coagulation test that may represent a certain interest to evaluate thrombosis risk as a high thrombin generation capacity seems to be an independent risk factor for recurrent thromboembolic events. Another point of interest to assess the thrombotic risk is the detection of autoantibodies recognizing domain 1 of β2Gp1 (aβ2GP1-dm1). These autoantibodies are strongly related correlated with thrombotic and pregnancy manifestations. Recently, a commercial chemiluminescence immunoassay (CLIA) for detection of aβ2GP1-dm1 became available on Acustar® analyzer (HemosIL Acustar®, Instrument Laboratory, Bedford, USA) to facilitate aβ2GP1-dm1 research.

The aim of this study is to evaluate two additional laboratory assays to improve the correlation between laboratory assays and the clinical thrombosis risk in patients with antiphospholipid (APL): thrombin generation assay and aβ2GP1-dm1. Each biological result (Antibodies to Domain 1 (Dm1) of β2-Glycoprotein 1 (aβ2GP1-dm1) and Thrombin Generation Test (TGT) parameters: endogen thrombin potential (ETP), lag time and time to peak) will be compared to the history of clinical thrombosis (venous or arterial thrombosis and/or obstetrical complications such as defined by the Saporro criteria updated with Sydney criteria in 2006) for each patient.

Inclusion Criteria:

• Adult patients with confirmed aPL-Abs (at least two positive determinations at least 12 week apart)
• Subject non opposition

Exclusion Criteria:

• Age < 18 years
• Patient under the protection of justice, under guardianship or under curatorship
• Patient with anticoagulant treatment, except heparin
• Clinically symptomatic liver disease, supported by e.g. diagnosis of cirrhosis, portal hypertension, ascites, PT superior or egal to 5 seconds above upper normal limit
• Platelet count < 100 G/L (giga/liter)
• Poor venous access
• Non confirmed suspicion of APS

150 adult patients with known aPL-Abs (Antiphospholipid antibodies) will be including in the study after collecting their informed consent.