What Is Lupus Anticoagulant?

Lupus anticoagulant (LAC) is an IgG or IgM antiphospholipid antibody that acts on phospholipids. In vivo and in vitro coagulation tests, phospholipids act as a template for the activation of prothrombinase complexes. Lupus anticoagulants are antibodies against phospholipids and are found in the blood of patients with a variety of autoimmune diseases. LAC can interfere with phospholipid-dependent coagulation or anticoagulation reactions, such as interference with F, F, FX, FII activation, and prolong PT and APTT in vitro. However, the complex of LAC and phospholipid protein can interfere with the activation of PC by the combination of thrombomodulin (TM) and thrombin, and compete with the APC / PS complex for the surface of phospholipids, causing APC to inactivate FVa and Fa and cause high blood levels. Coagulation status; LAC can also enhance platelet aggregation and inhibit fibrinolytic activity; therefore, patients with LAC positive are prone to thrombotic complications.

Basic Information

Lupus anticoagulant determination method

Activate FX with snake venom reagent, add Ca and low concentration of phospholipid, and observe the time of plasma clotting, which is called Russell snake venom time (RVVT). If RVVT is significantly prolonged, it may indicate a deficiency of coagulation factors or the presence of LAC. RVVT is shortened after adding normal plasma, which is a factor deficiency; if RVVT is still prolonged, it indicates the presence of LAC. After adding high concentration of phospholipid to neutralize LAC, the extended RVVT can be shortened or returned to normal, confirming the presence of LAC in plasma.

Clinical significance of lupus anticoagulant

Lupus anticoagulant is an antibody that prolongs the clotting time. It can be IgG or IgM or both. Found in SLE, spontaneous abortion, multiple thrombosis, thrombocytopenia, malignant tumors and drug-induced immune responses. In addition, lupus anticoagulants can also occur in patients with autoimmune diseases or lymphoproliferative malignant lesions, patients undergoing long-term psychotropic medications, and opportunistic infections and malignancies related to AIDS. If the test result is positive, you need to check again after a few weeks to see if the antibody is only short-term. The presence of lupus anticoagulants may lead to false positives for syphilis VDRL / RPR tests.

LAC in the test tube can prolong the clotting time, but no clinical signs of bleeding, but accompanied by a tendency to hyperthrombosis, and the simultaneous presence of anti-phospholipid antibodies (APL). If such patients are positive for APL, they are antiphospholipid syndrome.

Lupus anticoagulant normal reference range

33.3 to 39.3 seconds.