Coagulation Profile in Dogs

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Coagulation is the process of forming a blood clot. It takes many steps that must all go right in the body. The coagulation process involves the following components:

• A type of red blood cell called the platelet
• Endothelial cells lining the inside of an affected blood vessel
• Coagulation factors made in the liver that then circulate in the bloodstream and trigger formation of a blood clot

Without proper coagulation, the dog has a bleeding disorder, which is dangerous and can even be life-threatening.

A coagulation profile is a set of blood tests that can help a veterinarian determine whether a dog that's bleeding abnormally has a coagulation problem and which stage in the process is not functioning correctly. That can aid in diagnosing the problem and choosing the proper treatment.

Coagulation Tests in Dogs Evaluate Coagulation Factors

Thirteen substances circulate in the bloodstream and work together in a specific sequence to trigger blood clotting when there is an injury. An intrinsic and extrinsic pathway are each triggered and, eventually, those two sequences come together in a final, common pathway.

In the lab, blood tests measure the functioning of the three pathways.

Coagulation Tests in Dogs

The following coagulation tests are part of a diagnostic evaluation:

• Platelet count. This test looks at the number of circulating platelets in a blood sample. Platelets stick together to form the first patch at the site of an injury. They also help other coagulation factors join and stick in the area to help build a more permanent clot. Platelets are counted as part of a CBC, or complete blood count. Low numbers (thrombocytopenia) indicate a possible coagulation problem. Platelet count is often done as a screening test to determine whether other coagulation tests should be run. Note: Dogs with normal platelet numbers may still have a coagulation problem, including one that disrupts platelet function.
• Buccal mucosal bleeding time. This is another screening test done in the veterinary clinic to determine whether further coagulation testing is necessary. The veterinarian uses a device to make a tiny cut on the inside of the dog's upper lip. The doctor times how long it takes for the bleeding to stop. In a normal dog, a clot forms in less than 4 minutes.
• Activated clotting time (ACT). This is the third in-clinic screening test done to evaluate blood clotting. A small amount of the dog's blood is placed into a special tube containing a substance that activates both the extrinsic and intrinsic clotting pathways. The time it takes the blood inside the container to clot is then measured, and a prolonged time indicates a likely clotting problem.
• Activated partial thromboplastin time (PTT). This test is done at a veterinary laboratory. It evaluates the intrinsic and common clotting pathways.
• Prothrombin time (PT). This is another test done at a lab. It measures the function of the extrinsic and common clotting pathways.
• Thrombin time (TT). This lab test evaluates fibrinogen function. That clotting factor is used at the end of the common pathway to form the final fibrin clot over a wound.
• Von Willebrand factor (vWF). This test, done at a lab, evaluates how much von Willebrand factor is present in a dog's blood. vWF helps keep platelets sticky. Learn more: "Von Willebrand Disease."

Together with a CBC and basic blood chemistry results, a coagulation profile of PT, PTT, TT, and vWF can help a veterinarian determine which pathway of the coagulation system is malfunctioning. From there, further testing may be required to finish the diagnosis.

Interpretation of Coagulation Profile in Dogs

Interpreting the results of a coagulation profile is complicated and requires looking at all the test results together as well as keeping in mind physical exam and history results. A veterinarian uses a combination of results to develop a picture of what's going on inside the dog's body and reach a diagnosis and determine the best treatment course.

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