A-TH3 ASSAY - A test which measures the level of antithrombin III in the bloodstream. Conditions where there is a deficiency of this important protease inhibitor can result in a condition of hypercoagulation (increased blood clot formation). Normal values are: 0.20 to 0.45 mg/ml or more than 50% of the laboratory control value. Conditions that may have an associated low value of antithrombin III include: liver disease and DIC.