The Anti-Cardiolipin Antibodies test detects autoantibodies that target cardiolipin, a phospholipid found in the membranes of cells and platelets. These antibodies are associated with antiphospholipid syndrome (APS), an autoimmune disorder that increases the risk of abnormal blood clotting (thrombosis), recurrent pregnancy loss, and other vascular complications. The test measures levels of two types of anti-cardiolipin antibodies, IgG and IgM. Elevated levels can indicate a higher likelihood of blood clot formation or other symptoms of APS.

However, a single positive result may not confirm a diagnosis, as transient increases in these antibodies can occur due to infections or other temporary conditions. This test is commonly ordered when a patient has a history of unexplained blood clots, recurrent miscarriages, or other complications related to APS. It is also used as part of a broader diagnostic workup to evaluate autoimmune diseases like systemic lupus erythematosus (SLE).