Thrombin−Antithrombin Complex

CPT: 83520
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Expected Turnaround Time

3 - 9 days

Related Documents

For more information, please view the literature below.

Procedures for Hemostasis and Thrombosis: A Clinical Test Compendium

Specimen Requirements


Plasma, frozen


2 mL

Minimum Volume

1 mL


Blue-top (sodium citrate) tube


Blood should be collected in a blue-top tube containing 3.2% buffered sodium citrate.1 Evacuated collection tubes must be filled to completion to ensure a proper blood to anticoagulant ratio.2,3 The sample should be mixed immediately by gentle inversion at least six times to ensure adequate mixing of the anticoagulant with the blood. A discard tube is not required prior to collection of coagulation samples.4,5 When noncitrate tubes are collected for other tests, collect sterile and nonadditive (red-top) tubes prior to citrate (blue-top) tubes. Any tube containing an alternate anticoagulant should be collected after the blue-top tube. Gel-barrier tubes and serum tubes with clot initiators should also be collected after the citrate tubes. Centrifuge and carefully remove the plasma using a plastic transfer pipette, being careful not to disturb the cells. Transfer the plasma into a LabCorp PP transpak frozen purple tube with screw cap (LabCorp N° 49482). Freeze immediately and maintain frozen until tested. To avoid delays in turnaround time when requesting multiple tests on frozen samples, please submit separate frozen specimens for each test requested.

Please print and use the Volume Guide for Coagulation Testing to ensure proper draw volume.

Storage Instructions

Freeze; five freeze/thaw cycles are acceptable. Stable at room temperature or refrigerated for four hours.

Patient Preparation

Do not draw from an arm with a heparin lock or heparinized catheter.

Test Details


Assess thrombin formation and antithrombin consumption


Traumatic venipuncture, prolonged stasis, or inadequate centrifuging may invalidate results. Inadequate mixing of the patient sample and the citrate in the collection tube may result in falsely elevated levels. TAT levels may be elevated secondary to inflammation and microvascular thrombosis in surgical patients or those patients in acute distress.


TAT is measured by enzyme immunoassay using a sandwich technique. The patient sample containing TAT is incubated with antibodies against thrombin, and the unbound constituents are removed by washing. Enzyme conjugated antibodies to antithrombin are then added to the reaction, and the excess antibodies are removed by washing. The remaining (bound) enzymatic activity acts upon a chromophore and color development is proportional to the TAT in the sample.

Additional Information

Thrombin-antithrombin complexes (TAT) form covalently following thrombin generation and have a plasma half-life of 10 to 15 minutes. The presence of TAT indicates ongoing thrombin formation and the consumption of antithrombin. Upon activation of coagulation, antithrombin complexes with thrombin as well as other serine proteases. Complex formation is greatly enhanced by the presence of heparin or other glycosaminoglycans. The reaction initially is reversible, but becomes irreversible following the formation of a covalent bond between antithrombin and thrombin. This binding results in complete inhibition of thrombin's activity. Elevated levels of TAT may be associated with advancing age, pregnancy, septicemia, disseminated intravascular coagulation, multiple trauma, acute pancreatitis, acute and chronic leukemia, preëclampsia, acute and chronic liver disease, and other predisposing causes of thrombosis. Increased levels are also reported during heparin and fibrinolytic therapy. TAT levels are markedly reduced in the first 24 hours after receiving oral anticoagulants. The TAT assay can detect the intravascular generation of thrombin and provides valuable information in the diagnosis of thrombotic events. Decreasing TAT levels can also indicate the resolution of a thrombotic event. A normal TAT level in the presence of an elevated D-dimer may indicate an old thrombus. Elevated TAT measurements may be accompanied by increased levels of prothrombin fragment 1+2, fibrinopeptide A, fibrin(ogen) degradation products, and D-dimer. D-dimer has greater sensitivity for detection of deep venous thrombosis.


1. Adcock DM, Kressin DC, Marlar RA. Effect of 3.2% vs 3.8% sodium citrate concentration on routine coagulation testing. Am J Clin Pathol. 1997 Jan; 107(1):105-110. 8980376
2. Reneke J, Etzell J, Leslie S, Ng VL, Gottfried EL. Prolonged prothrombin time and activated partial thromboplastin time due to underfilled specimen tubes with 109 mmol/L (3.2%) citrate anticoagulant. Am J Clin Pathol. 1998 Jun; 109(6):754-757. 9620035
3. National Committee for Clinical Laboratory Standardization. Collection, Transport, and Processing of Blood Specimens for Coagulation Testing and General Performance of Coagulation Assays; Approved Guideline. 5th ed. Villanova, Pa: NCCLS; 2008. Document H21-A5:28(5).
4. Gottfried EL, Adachi MM. Prothrombin time and activated partial thromboplastin time can be performed on the first tube. Am J Clin Pathol. 1997 Jun; 107(6):681-683. 9169665
5. McGlasson DL, More L, Best HA, Norris WL, Doe RH, Ray H. Drawing specimens for coagulation testing: Is a second tube necessary? Clin Lab Sci. 1999 May-Jun; 12(3):137-139. 10539100


Boisclair MD, Lane DA, Wilde JT, Ireland H, Preston FE, Ofosu FA. A comparative evaluation of assays for markers of activated coagulation and/or fibrinolysis: Thrombin-antithrombin complex, D-dimer, and fibrinogen/fibrin fragment E antigen. Br J Haematol. 1990 Apr; 74(4):471-479. 2189490
Boneu B, Bes G, Pelzer H, Sié P, Boccalon H. D-Dimer, thrombin antithrombin III complexes, and prothrombin fragments 1+2: Diagnostic value in clinically suspected deep vein thrombosis. Thromb Haemost. 1991 Jan 23; 65(1):28-31. 2024237
Fareed J, Hoppensteadt DA, Leya F, Iqbal O, Wolf H, Bick R. Useful laboratory tests for studying thrombogenesis in acute cardiac syndromes. Clin Chem. 1998 Aug; 44(8 Pt 2):1845-1853. 9702994
Speiser W, Mallek R, Koppensteiner R, et al. D-Dimer and TAT measurement in patients with deep venous thrombosis: Utility in diagnosis and judgment of anticoagulant treatment effectiveness. Thromb Haemost. 1990 Oct 22; 64(2):196-201. 2125371


Order Code Order Code Name Order Loinc Result Code Result Code Name UofM Result LOINC
500012 Thrombin Antithrombin Complex 500013 Thrombin Antithrombin Complex ng/mL 14182-0

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