Non-classification criteria

Antiphospholipid syndrome (APS) is characterized by vascular thrombosis and/or pregnancy complications in association with the presence of antiphospholipid antibodies (aPL), i.e., anticardiolipin (aCL), anti-beta2-glycoprotein I (anti-β2GPI), and lupus anticoagulant (LA). In addition to these three aPL assays, a number of other laboratory tests have been proposed for APS diagnosis: antiprothrombin antibodies, anti-domain I and IV/V antibodies, anti-phosphatidylethanolamine antibodies, antibodies against other anionic phospholipids (such as phosphatidylserine, phosphatidylinositol, or phosphatidic acid), and antibodies against annexin A5 and annexin A2. aCL/anti-β2GPI and anti-annexin A5 antibodies of the IgA isotype have been also suggested. However, these additional assays are not included in the classification criteria, due to their poor sensitivity or specificity. Moreover, besides arterial and venous thrombosis, a number of clinical manifestations that can be only in part explained by the thrombophylic state have been described: thrombocytopenia, heart valve disease, livedo reticularis, skin ulcers, nephropathy, and non-ischemic neurological features. These manifestations are associated with APS, but are not included in the clinical classification criteria.