Lupus Anticoagulant

The Lupus Anticoagulant test (also known as lupus inhibitor testing) is used in the evaluation of unexplained thrombosis and recurrent pregnancy loss. It assists in the workup of a prolonged activated partial thromboplastin time (aPTT), helping distinguish a lupus anticoagulant from a specific coagulation factor inhibitor, and it can be used to confirm LA after an initial screening result. LA assessment may include LA‑sensitive aPTT (PTT‑LA) and DRVVT‑based approaches. In the diagnostic assessment of antiphospholipid syndrome, LA testing is interpreted in conjunction with anticardiolipin and anti–beta‑2 glycoprotein I antibody assays.

Lupus anticoagulants are autoantibodies against phospholipids and/or phospholipid‑associated proteins that prolong phospholipid‑dependent coagulation assays in vitro, yet are paradoxically linked to a prothrombotic state in vivo. Initially described in systemic lupus erythematosus, they also occur with other autoimmune disorders, infections, malignancy, and certain drug exposures. LA increases the risk of both venous and arterial thrombosis and is associated with pregnancy morbidity, including fetal loss, with particular impact during the second and third trimesters. No single assay defines LA. Detection relies on a sequence of phospholipid‑dependent screening tests (such as DRVVT or an LA‑sensitive aPTT), followed by mixing studies and confirmatory procedures that demonstrate correction with excess phospholipid, establishing phospholipid dependence. LA constitutes one of the three laboratory criteria for antiphospholipid syndrome, together with anticardiolipin and anti–beta‑2 glycoprotein I antibodies.