Anti-Phosphatidylserine antibodies (IgG, IgM, and IgA) are associated with the same clinical manifestations as aCL. Phosphatidylserine is found in the membranes of platelets and endothelial cells, and participates in the coagulation cascade. Testing for antibodies to phosphatidylserine provides not only more clinically relevant results, but also additional information to assess the risk of thrombosis.