What is Lupus anti-coagulant?

Lupus anticoagulant (LA) is an autoantibody that causes incorrect results in blood coagulation assays.

It prolongs the plasma clotting time measured in activated partial thromboplastin time (APTT)[/activated clotting time (ACT)] due to abnormal interference/blockade. It, typically, does not prolong prothrombin time (PT) or cause bleeding**, except in rare instances.

- An individual may have an LA in the absence of symptoms or any associated autoimmune disorder.

- LA is more frequently found in asymptomatic family members of patients with lupus than in the normal population.

Although LA is commonly called an "antibody," it is not directed at an intrinsic coagulation protein but rather at a complex comprising negatively charged phospholipid (PL), calcium, and a PL-binding protein such as prothrombin, protein C, or annexin II.

An acquired inhibitor, not present at birth, usually of immunoglobulin G (IgG) class, and directed against negatively charged PL-protein complexes on the surface of activated platelets, and against beta2-glycoprotein-1 (apolipoprotein H), is termed lupus anticoagulant.