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Thrombin Time

February 15th, 2021


The thrombin time (TT) is not routinely performed as part of a coagulation screen.
    • Normal Range

    • <24 seconds
  • Important Lab Points

  • Performed by adding thrombin to a plasma sample.
  • Tests only the final step of fibrin clot formation.
  • If the TT is prolonged, a reptilase test is also performed to distinguish between causes.
Diluted thrombin time may have a role in the monitoring of factor IIa inhibitors (e.g. dabigatran).

Prolonged Thrombin Time

  • Interpretation

  • Prolonged reptilase - fibrinogen defects, fibrin degradation products
  • Normal reptilase - heparin, factor IIa inhibitors
  • Causes of Prolonged Thrombin Time

  • Fibrinogen defects - hypofibrinogenaemia, afibrogenaemia, dysfibrinogenaemia
  • Fibrin degradation products (e.g. in DIC)
  • Factor IIa inhibitors (e.g. dabigatran)
  • Heparin
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