Why Is My Dog Or Cat's Thrombin Clot Time CT Increased ?













Ron Hines DVM PhD

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Your Pet's Thrombin Clot Time /TC = A Measure Of Bleeding Tendency = TCT, Thrombin Time,TT

This is one of a group of tests that investigate why your dog or cat ’s blood clotting mechanism might be defective. You veterinarian might order this test if he/she is suspicious that you pet is bleeding due to a fault in its complex clotting mechanism. Perhaps, you and your veterinarian are faced with unexplained anemia in your dog or cat. Perhaps your pet bled excessively during surgery or after an accident. Perhaps blood has repeatedly been seen in the pet's stool or urine and other more common causes have been ruled out.

Because the clotting of blood is such a complex process (the coagulation cascade) with so many different stages or steps and the interplay of many chemicals and cells, a series of tests might be required to determine exactly what is wrong. Some of these other tests are thrombocyte count, prothrombin time (PT), partial thromboplastin time (PTT/APTT), fibrinogen level, and, perhaps, a d-dimer test.

Thrombin is a blood enzyme protein (a protease) that is formed from prothrombin, produced in your pet’s liver. It activates platelets circulating in your pet's blood to stick together and helps convert fibrinogen into fibrin to seal off bleeding blood vessels.

At one time, this test was a popular way to monitor anticoagulant therapy (warfarin) in people who had developed blood clots that led to a heart attack. Cats and dogs do not get those sort of heart attacks. In humans, the TCT has been replaced by newer, more sophisticated testing methods.



Reasons Why Your Pet’s Thrombin Clot Time Could Be Prolonged (Increased) :

The most common cause is a deficiency in fibrinogen. That is usually due to liver disease.

TCT can also be prolonged if pets receive heparin anticoagulant. Heparin has been given to dogs and cats in an attempt to clear clots from their lungs (pulmonary embolisms) and in cases of severe shock that cause clots to form throughout the circulatory system (disseminated intravascular coagulation, DIC). Heparin is also occasionally given to cats that developed blood clots blocking the flow of blood to their rear legs (the saddle thrombi of hypertrophic cardiomyopathy or HCM).

Some forms of inherited hemophilia also prolong TCT time (eg hypofibrinogenemia, factor XIII deficiency?).

Rat and mouse poisons (warfarin-type) do not increase TCT in pets.

Why Would My Pet’s Thrombin Clot Time Be Decreased (faster) ?

Anabolic steroids, such as stanozolol, (Winsterol) and testosterone have been known to shorten Thrombin Clot Time. Certain rare inherited fibrinogen defects (dysfibrinogenemias) are said to do this as well.

Complementary Tests :

Those mentioned at the beginning of this page, liver function tests if a fibrinogen deficiency exists, FDP assay (Fibrinogen degradation products)