Classification criteria for antiphospholipid syndrome (APS) require IgG or IgM isotypes of the anticardiolipin (aCL) antibodies, anti-β2-glycoprotein I (anti-β2GPI) antibodies, and/or the lupus anticoagulant (LA) to satisfy the laboratory criterion for disease definition.1 Over the past years several ‘non-criteria’ antiphospholipid antibodies (aPL), directed to proteins of the coagulation cascade (i.e., prothrombin and/or phosphatidylserine–prothrombin complex) or to specific domains of β2GPI have been focused upon.2,3. Here, F2 is linked to antiphospholipid syndrome.