HERMANN TEST CODE: 26-00470
CPT CODE: 85301
SPECIMEN REQUIREMENT: 5 mL blood (minimum 4.5 ml), blue top tube (sodium citrate), mixed well.
TEST AVAILABILITY: Sent out by Hermann Laboratory to Colorado Coagulation Reference Laboratory. Reporting time in less than 7 days.
METHODOLOGY: Radial Immunodiffusion (RID)
CLINICAL UTILIZATION: Diagnosis of Dysfunctional Antithrombin
REFERENCE RANGE: 22-39 mg/dL
INTERPRETATION:
Antithrombin (AT III) is a plasma protein that inhibits thrombin by binding to its active site. Heparin exerts its anticoagulant effect by accelerating the binding of AT III to thrombin. Congenital AT III deficiency may have two different forms: (a) decreased synthesis of a normal AT III molecule, and (b) production of dysfunctional AT III. Both forms are inherited as autosomal dominant. These two forms are clinically indistinguishable and are both characterized by a predisposition to thrombosis. Acquired deficiency of AT III may occur in: Disseminated Intravascular Coagulation (DIC), deep vein thrombosis, pulmonary embolism, diffuse veno-occlusive disease.
Without ongoing thrombotic complications, patients with AT III deficiency usually have normal coagulation screen tests (PT, PTT, Fibrinogen, Thrombin Time, Platelet Count). Deficiency of AT III should initially be investigated with an AT III functional assay. If the AT III functional assay is normal, AT III deficiency can be excluded. Only an abnormal functional AT III assay requires further testing with AT III antigen assay to rule out dysfunctional AT III.
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