Lupus anticoagulant is an immunoglobulin[1] that binds to phospholipids and proteins associated with the cell membrane.
Investigators speculate that the antibodies interfere with phospholipids used to induce in vitro coagulation.
[3][4] Both words in the term "lupus anticoagulant" can be misleading: The main indication for testing for lupus anticoagulant is a suspected antiphospholipid syndrome, whose main manifestations are blood clots (thrombosis) in both arteries and veins as well as pregnancy-related complications such as miscarriage, stillbirth, preterm delivery, and severe preeclampsia.
[8] An aPTT is generally included in a differential diagnosis in vague symptoms, and is a non-specific test of coagulation.
In contrast, the prothrombin time (PT), another non-specific coagulation test, is normally unaffected by lupus anticoagulant.
The Sapporo criteria specify that both serological and functional tests must be positive to diagnose the antiphospholipid antibody syndrome.