Cardiolipin Antibodies, IgG

Cardiolipin Antibodies, IgG (IgG anticardiolipin; aCL IgG) aids the diagnosis of antiphospholipid syndrome and contributes to the differential diagnosis of thrombophilia. It is ordered to assess unexplained arterial or venous thromboembolism, recurrent pregnancy loss and related obstetric morbidity, and to evaluate suspected secondary antiphospholipid syndrome in systemic lupus erythematosus. When combined with the clinical context and results of other antiphospholipid assays such as lupus anticoagulant and anti–beta-2 glycoprotein I, this test may inform risk estimation for recurrent thrombosis or future pregnancy complications.

IgG anticardiolipin antibodies are part of a heterogeneous antiphospholipid antibody family that recognizes protein–phospholipid complexes and can promote thrombosis via endothelial activation, platelet activation, and disruption of coagulation pathways. Antiphospholipid syndrome presents with arterial and/or venous thrombosis and pregnancy morbidity, and is defined immunologically by persistent positivity for anticardiolipin IgG and/or IgM, anti–beta-2 glycoprotein I, or lupus anticoagulant on at least two occasions separated by 12 or more weeks. Thrombotic events may be unprovoked or occur with triggers such as surgery, trauma, pregnancy, or exposure to estrogen, and can involve either venous or arterial circulation. Obstetric manifestations include recurrent early pregnancy loss, fetal death, preeclampsia, placental insufficiency, and preterm delivery not otherwise explained. Higher anticardiolipin IgG titers (e.g., >40 GPL units) correlate with increased risk of ischemic stroke and recurrent pregnancy loss, and increasing titers generally correspond to greater thrombotic risk.