Hemostasis Reference Laboratory

Antithrombin III (Activity)

• Transaction Code: 3230-01
• CPT Code (Suggested): 85300

Antithrombin III is a cofactor for vessel wall heparin or therapeutic heparin that inhibit the coagulation cascade by inactivating several activated coagulation enzymes (e.g., factors IIa, IXa and Xa). Antithrombin III level is measured by chromogenic substrate assay. Levels are reduced in hereditary antithrombin III deficiency, an autosomal dormant disorder that is associated with a thrombotic tendency. Acquired causes of antithrombin III deficiency include liver disease, disseminated intravascular coagulation (DIC), nephrotic syndrome, massive thrombosis, oral contraceptives, and heparin therapy.

• Sample Required: 0.5 ml frozen plasma x4 or (2) 3.2% sodium citrated tubes, 5 ml each.
• See Sample Requirements when ordered with other tests.
• Normal Range: >75%
• Analytic Time: Within 5 working days