The Cardiolipin IgG Antibody test is a blood test that measures the level of IgG antibodies to cardiolipin in the blood. Cardiolipin is a phospholipid found in the inner mitochondrial membrane of cells. The test is typically used to help diagnose autoimmune disorders, such as antiphospholipid syndrome (APS), which is a condition where the immune system mistakenly attacks phospholipids in the body. In APS, IgG antibodies to cardiolipin can cause blood clotting and increase the risk of stroke, heart attack, and other thrombotic events. The Cardiolipin IgG Antibody test may also be used to monitor the effectiveness of treatment for APS and to assess the risk of thrombotic events in patients with other autoimmune disorders. The test is performed by taking a blood sample and sending it to a laboratory for analysis. Results are typically reported as a numerical value or a positive/negative result, depending on the laboratory’s reference range.