Antithrombin Test - Reference Range

Antithrombin is a natural anticoagulant that inhibits the activated coagulation factors thrombin (factor IIa), factor Xa, and, to a lesser extent, factor XIa and factor IXa.

The reference range of antithrombin varies by age, as follows:

  • Newborn: 60%-90%
  • Children and adults: 80%-120%
  • Plasma concentration: 0.15-0.2 mg/mL

An increased antithrombin level is not a clinical problem. Inherited types of antithrombin deficiency are as follows:

  • Type I – Decreased functional and immunological antithrombin level
  • Type II – Decreased functional antithrombin activity, while protein concentration is normal

Keywords: Antithrombin (Activity and Antigen); AT 3; AT III; Functional Antithrombin III

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