Lupus anticoagulant

The Lupus anticoagulant test (also referred to as DRVVT, PTT‑LA, or lupus inhibitor testing) is used to investigate unexplained venous or arterial thrombosis and pregnancy loss. It is applied to determine whether a prolonged aPTT reflects the presence of LA rather than a specific coagulation factor inhibitor, using a sequence of screening, mixing, and confirmatory studies. LA testing is also performed to confirm the presence of a lupus anticoagulant and, together with anticardiolipin and anti–beta‑2 glycoprotein I antibody assays, to support the laboratory evaluation for antiphospholipid syndrome.

Lupus anticoagulants are autoantibodies that target phospholipids and/or the proteins that bind them. These antibodies prolong phospholipid‑dependent coagulation assays in vitro, yet their presence correlates with a higher incidence of venous and arterial thrombosis and with pregnancy morbidity. The term “lupus anticoagulant” (also known as lupus inhibitor) reflects their laboratory effect rather than clinical behavior. No single assay definitively identifies LA. Detection relies on a staged approach that includes phospholipid‑dependent screening tests, mixing studies with normal plasma, and confirmatory procedures; commonly used components are the dilute Russell viper venom time (DRVVT) and an LA‑sensitive activated partial thromboplastin time. LA may be transient or persistent and is encountered in systemic autoimmune disease, infections, inflammatory conditions, and malignancy. It represents one of the three antiphospholipid antibodies included in the classification criteria for antiphospholipid syndrome.