F2 and antiphospholipid syndrome: Antiphospholipid syndrome (APS) is a thromboinflammatory autoimmune disease that is characterized by the presence of persistently positive antiphospholipid (aPL) antibodies measured by immunoassays for anticardiolipin and anti-β-2-glycoprotein I (anti-β2GPI) antibodies or by the lupus anticoagulant functional screen, which detects a variety of aPL antibody species including anti-phosphatidylserine/prothrombin (anti-PS/PT) antibodies (1, 2).