Partial Thromboplastin Time (PTT) in Cats
Clotting, or coagulation, of blood is a protective mechanism to arrest bleeding. Many different proteins are involved this multi-step process. An abnormality occurring at any of the various steps of coagulation process will result in prolonged bleeding. Without treatment, bleeding disorders may lead to death of the animal.
One of the tests used to determine a possible cause of a bleeding disorder is the partial thromboplastin test. Evaluation of the "partial thromboplastin time" is indicated in any pet with a suspected coagulation or bleeding problem. This test is also performed before procedures in which there is a concern about normal clotting, such as a liver biopsy.
There are no contraindications to performing this test. However, in pets with known coagulation problems, taking the blood sample may cause excessive bleeding at the venipuncture site. In such cases, special care should be taken by drawing blood from a small vein and applying appropriate and prolonged pressure at the site.
What Does a Partial Thromboplastin Time Reveal?
The partial thromboplastin time (PTT) measures the intrinsic clotting time in plasma. It is taken used to evaluate the adequacy of certain coagulation proteins. Specifically, the PTT test measures deficiencies of the intrinsic and common coagulation pathways. Of the more than 12 clotting proteins involved in forming a blood clot, PTT tests Factors XII, XI, X, IX, VIII, V, II and I. Several of these clotting factors need adequate levels of vitamin K to function properly. The normal partial thromboplastin time in dogs and cats is less than 20 seconds but this can vary from laboratory to laboratory. 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, a partial thromboplastin time may be run at a local human hospital. The test typically takes less than 10 minutes to run once the blood is available. If submitted to an outside laboratory, the test results may not be available for up to 1 to 2 days.
Is a Partial Thromboplastin Time Painful?
The only pain involved is associated with the collection of the blood sample. The pain experienced varies from individual to individual.
Is Sedation or Anesthesia Needed for a Partial Thromboplastin Time?
Neither sedation nor anesthesia is needed in most patients. However, for pets that resent and resist blood sampling, tranquilization can be helpful.