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Thrombin Time

Does this test have other names?

Thrombin clotting time, TCT

What is this test?

Blood clotting is an important step in healing from an injury, such as a cut. Forming a blood clot is a complicated process. It involves many blood components that must interact in a specific order.

Thrombin time is a measure of how long the blood's plasma, or the liquid portion of the blood, takes to form a clot. This test gives information about how well one particular blood component called fibrinogen is working. 

Why do I need this test?

Your healthcare provider may order this test if your blood does not seem to be clotting properly. Abnormal results of the thrombin time test may mean that you may have low or high levels of fibrinogen, or that your fibrinogen is not working properly.

This can be because of:

  • Inherited conditions that lead to low fibrinogen or fibrinogen disorders

  • Liver diseases such as cirrhosis, hepatitis, and liver cancer

  • Cancers such as kidney cancer (renal carcinoma) or multiple myeloma

  • Certain other health conditions, including lupus and ulcerative colitis

  • Surgery that uses fibrin glue created from cow sources. This may cause the body to develop antibodies against fibrinogen.

  • Disseminated intravascular coagulation, a condition in which your body uses more fibrinogen

Certain medicines can also lead to a longer thrombin time,. These include:

  • Heparin

  • Warfarin

  • Hirudin

  • Bivalirudin

  • Argatroban

Symptoms of fibrinogen problems include:

  • Excessive bleeding or bruising

  • Pregnancy problems. These include repeated miscarriages early in pregnancy, and abnormal bleeding after delivery.

What other tests might I have along with this test?

Your healthcare provider may recommend other tests to measure your blood's clotting ability. These include:

  • Reptilase time. Like thrombin time, this test measures the conversion of fibrinogen to fibrin. It shows if an unusually long thrombin time is because of heparin.

  • Prothrombin time. This test gives information about fibrinogen and other components that play a role in clot formation. It's also used to measure the effects of warfarin, a blood-thinning medicine.

  • Activated partial thromboplastin time. This test also gives information about numerous factors involved in blood clotting and is used to measure the effects of heparin treatment.  

What do my test results mean?

Many things may affect your lab test results. These include the method each lab uses to do the test. Even if your test results are different from the normal value, you may not have a problem. To learn what the results mean for you, talk with your healthcare provider. 

The lab technician places thrombin from humans or cows in your plasma sample and records the number of seconds needed for it to form a clot. A normal thrombin time is 11.3 to 18.5 seconds.

A longer thrombin time can mean low fibrinogen, high fibrinogen, or fibrinogen that's not working properly. It can also be because of medicines that affect blood clotting, such as heparin, argatroban, hirudin, or hirulog. 

A longer thrombin time can be caused by proteins in the blood from the health conditions multiple myeloma or amyloidosis. Or it could be caused by antibodies that developed from earlier exposure to bovine thrombin. 

How is this test done?

The test requires a blood sample, which is drawn through a needle from a vein in your arm. The sample is placed in a tube containing a chemical that keeps it from clotting.

Does this test pose any risks?

Taking a blood sample with a needle carries small risks that include bleeding, infection, bruising, and a sense of lightheadedness. When the needle pricks your arm, you may feel a slight sting or pain. Afterward the site may be sore.

What might affect my test results?

Some medicines that alter blood clotting will affect your test results, including heparin and warfarin.

How do I get ready for this test?

Tell your healthcare provider if you're taking any medicines, especially those that affect your blood's ability to clot. Also tell your provider about any over-the-counter medicines, vitamins, herbs, or supplements you are taking, too. Also discuss any health conditions you have and any history of unusual bleeding.  

Medical Reviewers:

  • Sather, Rita, RN
  • Walton-Ziegler, Olivia, MS, PA-C