Partial Thromboplastin Time (PTT) in Dogs

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Clotting, or coagulation, of blood is a protective mechanism that arrests bleeding. Many different proteins are involved in the coagulation process in dogs and other animals. Abnormality at any of the many stages in coagulation cascade will result in prolonged bleeding. Without treatment, bleeding disorders may sometimes lead to death of the dog.

One of the tests used to help determine a cause for a bleeding disorder is the partial thromboplastin test. Measurement of the partial thromboplastin time (PTT) is indicated in any pet suspected of having a coagulation problem. PTT is also determined before procedures in which there is a concern about blood clotting, such as a liver biopsy.

A PTT test is commonly performed in conjunction with another clothing test called the PT. It is common to hear the term PT and PTT used together when discussing a dogs clotting time. 

There are no contraindications to performing this test. In pets with coagulation problems, it is possible that collection of the blood sample may result in excessive bleeding. In such animals, special care must be taken by drawing the blood from a small vein and applying appropriate and prolonged pressure at the venipuncture site.

What Does a Partial Thromboplastin Time (PTT) Reveal in Dogs?

PTT is a measure of the time it takes for plasma to clot. It is used to evaluate the adequacy of certain coagulation proteins and identifies deficiencies of the intrinsic and common coagulation pathways. Of the more than 12 clotting proteins involved in normal blood clotting, the PTT tests Factors XII, XI, X, IX, VIII, V, II and I. Several of these clotting factors depend on vitamin K to function. Normal PTT time in dogs and cats is less than 20 seconds, but this can vary from lab to lab. Values greater than 20 seconds indicate a potential bleeding disorder. The most common cause of a prolonged partial thromboplastin time is poisoning with an anticoagulant rodenticide.

How Is a Partial Thromboplastin Time Done?

In order to perform a partial thromboplastin time, your veterinarian must draw a blood sample, which is placed in a special glass tube. This sample is then submitted to a laboratory for analysis. Some veterinary clinics, and most veterinary emergency facilities, have the ability to perform this test in their hospital. Others rely on outside laboratories. In an emergency situation, a partial thromboplastin time may be run at a local human hospital for rapid results. The test typically takes less than 10 minutes to run once the blood is available. If submitted to an outside laboratory, the test results should be available in 1 to 2 days.

Is a Partial Thromboplastin Time Painful to Dogs?

The only pain involved is associated with the collection of the blood sample. The pain experienced during blood sampling varies from individual to individual, as it does in people.

Is Sedation or Anesthesia Needed for a Partial Thromboplastin Time?

Neither sedation nor anesthesia is needed in most patients. However, in pets that resent having blood taken, tranquilization may be indicated.

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