Merck Manual

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Antithrombin Deficiency

By

Michael B. Streiff

, MD, Johns Hopkins University School of Medicine

Reviewed/Revised Aug 2023
View PATIENT EDUCATION

Because antithrombin inhibits thrombin and factors Xa, IXa, and XIa, deficiency of antithrombin predisposes to venous thrombosis.

Antithrombin is a plasma protein that inhibits thrombin and factors Xa, IXa, and XIa, thereby inhibiting thrombosis.

General reference

  • 1. Pabinger I, Thaler J. How I treat patients with hereditary antithrombin deficiency. Blood 2019;134(26):2346-2353. doi:10.1182/blood.2019002927

Diagnosis of Antithrombin Deficiency

Laboratory testing is done for patients with an unexplained blood clot and involves quantification of the capacity of patient plasma to inhibit thrombin in the presence of heparin. Heparin normally inhibits coagulation by accelerating inactivation of thrombin by antithrombin. In patients with antithrombin deficiency, inactivation of thrombin is reduced. The residual thrombin in the test mixture is inversely proportional to the functional antithrombin concentration in the patient's plasma. Antithrombin protein levels also can be measured with immunologic assays, but these tests only measure the amount of antithrombin protein in the sample and cannot assess the function of this protein. Since rare patients with antithrombin deficiency express dysfunctional antithrombin proteins, activity assays are favored over antigen assays for the diagnosis of antithrombin deficiency.

Treatment of Antithrombin Deficiency

  • Anticoagulation

Direct oral anticoagulants or warfarin can be used for long-term anticoagulation in patients with antithrombin deficiency and venous thromboembolism (1, 2 Treatment references Because antithrombin inhibits thrombin and factors Xa, IXa, and XIa, deficiency of antithrombin predisposes to venous thrombosis. (See also Overview of Thrombotic Disorders.) Antithrombin is... read more ).

Treatment references

  • 1. Campello E, Spiezia L, Simion C, et al. Direct Oral Anticoagulants in Patients With Inherited Thrombophilia and Venous Thromboembolism: A Prospective Cohort Study. J Am Heart Assoc 2020;9(23):e018917. doi:10.1161/JAHA.120.018917

  • 2. Pabinger I, Thaler J. How I treat patients with hereditary antithrombin deficiency. Blood 2019;134(26):2346-2353. doi:10.1182/blood.2019002927

Drugs Mentioned In This Article

Drug Name Select Trade
Hepflush-10 , Hep-Lock, Hep-Lock U/P, Monoject Prefill Advanced Heparin Lock Flush, SASH Normal Saline and Heparin
Coumadin, Jantoven
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NOTE: This is the Professional Version. CONSUMERS: View Consumer Version
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