Testing for predisposing congenital factors includes specific assays that measure the quantity or activity of natural anticoagulant molecules in plasma, and screening for specific gene defects, as follows: Clotting assay for lupus anticoagulant Clotting assay for resistance to activated protein C Genetic test for factor V Leiden Genetic test for prothrombin gene mutation (G20210A) Functional assay of antithrombin Functional assay of protein C Functional assay of protein S Antigenic assays of total and free protein S Measurement of plasma homocysteine levels Immunoassays for antiphospholipid antibodies Treatment of Thrombotic Disorders Treatment is summarized elsewhere in THE MANUAL specific to the location of the thrombus.