Frequency and Clinical Significance Anti-PS/PT Antibodies in Patients with Antiphospholipid Syndrome - Single Centre Observational Study in the United Kingdom.

Antiphospholipid syndrome (APS) is an acquired autoimmune disease, defined by the presence of persistently positive antiphospholipid antibodies (aPLs) on two or more occasions at least 12 weeks apart, in association with the clinical occurrence of thrombotic and/or obstetric complications.[1] Although current classification criteria for APS,[1] often also used as surrogate diagnostic criteria, include only lupus anticoagulant (LA), IgG and IgM anticardiolipin antibodies (aCL) and anti-β2-glycoprotein I (anti-β2GPI) antibodies, a broad group of autoantibodies against various targets are present in APS patients, which may variably contribute to pathogenesis of the disorder. Of these numerous autoantibodies, anti-phosphatidylserine/prothrombin antibodies (anti-PS/PT) that target the anionic phospholipid phosphatidylserine and the procoagulant plasma protein prothrombin, have recently become of particular interest.[2] [3] Similar to cardiolipin that forms complexes with β2GPI, PS/PT is a complex composed of phosphatidylserine and prothrombin. Several studies have shown an enhanced performance of anti-PS/PT compared with antibodies against prothrombin alone (aPT) in the diagnosis of APS[4] [5] and inclusion of anti-PS/PT may contribute to more accurate risk stratification in this heterogeneous disorder.