The Beta-2 Glycoprotein 1 IgM antibody test measures the presence of IgM class antibodies directed against beta-2 glycoprotein 1 in the blood. Beta-2 glycoprotein 1 is a plasma protein involved in the regulation of blood coagulation. The presence of these antibodies is associated with autoimmune disorders, particularly antiphospholipid syndrome (APS), which can increase the risk of blood clots, recurrent miscarriages, and other vascular complications.