The Anti-Cardiolipin IgG (aCL IgG) Test is a crucial blood assay used to detect and measure Immunoglobulin G (IgG) antibodies that specifically target cardiolipin, a type of phospholipid found in cell membranes. This test is a cornerstone in screening for Antiphospholipid Syndrome (APS), a systemic autoimmune disorder associated with an increased risk of thrombosis (blood clots) and complications during pregnancy.