Many tests for hypercoaguability are not reliable immediately after a thrombotic event or while the patient is on anticoagulant therapy. During this acute period, the only reliable analyses are for a lupus anticoagulant, Factor V Leiden, and the Prothrombin 20210A gene mutation. When the patient is stable and off any anticoagulant treatment, the following analysis may be appropriate: Protein C, Protein S, Antithrombin III. Protein C and Protein S levels should not be drawn when a patient is on the anticoagulant, coumadin.