The Lupus Anticoagulant (LA) test is a blood assay designed to detect autoimmune antibodies (from the antiphospholipid antibody group) that increase the risk of abnormal blood clot formation (thrombosis) by interfering with coagulation factors. This test is primarily used to evaluate patients with recurrent thrombosis, recurrent miscarriages (especially in the second or third trimester), or to diagnose Antiphospholipid Syndrome (APS).
The methodology involves a multi-phase approach:
Screening tests (e.g., aPTT or dRVVT) to detect prolonged clotting times.
Confirmatory tests (e.g., phospholipid correction) if screening results are abnormal.
Positive results indicate antibodies targeting phospholipids or associated proteins. Despite its name, this test:
Is not exclusive to systemic lupus erythematosus (SLE).
May occur in other autoimmune disorders, infections, or transiently in healthy individuals.
Interpretation requires:
Concurrent testing for other antiphospholipid antibodies (e.g., anti-cardiolipin, anti-β₂-glycoprotein I).
Exclusion of interfering factors (e.g., anticoagulant medications).
Definitive APS diagnosis requires:
Repeat positive testing after 12 weeks.
Clinical symptoms (thrombosis/pregnancy morbidity).
