Why Is My Dog von Willibrand Factor Positive ?

(Quite Rare - But Has Occurred In Cats)

To see what normal blood and urine values are for your pet, go here

For an explanation of causes of most abnormal blood and urine tests go here

To see how tests are often grouped, go here

For an extensive list of health problems that can delay blood clotting in your pet, go here

Ron Hines DVM PhD

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von Willibrand Factor

vWf, vWD

This is a test for a genetic bleeding disorder in dogs, but it has been reported (rarely) in cats.

There are several different subtypes or levels of vWD disease. All of them are due to insufficient or defective amounts of a blood clotting ingredient called von Willebrand factor (vWF) that is necessary for blood platelets (thrombocytes) to stick together and help form a blood clot.

The problem is most common in Doberman pinschers, although other breeds are occasionally affected (eg Golden Retrievers, Shetland Sheepdogs, Rottweilers, Miniature Schnauzers, German Shepherds, German Short-Haired Pointers, Standard Poodles, and Scottish Terriers). vWF occasionally occurs in cats as well.

This problem varies in severity and many animals that are mild to moderately deficient in vWf never have visible health problems.

The vWF test can be one that measures for adequate von Willebrand’s factor in a sample of your pet’s blood.

But it can also be a genetic DNA test on a swab from your pet’s mouth that determines if your dog is free of the genetic defect that causes the problem. That test will also identify silent carriers. It is not completely understood how the genetic defect inherits (it could be an autosomal recessive trait but could also be an autosomal dominant trait, with incomplete penetrance).

There are four reasons a vWF test is usually performed:

You are a breeders want to be sure that your breeding stock is free from the genetic defect that causes this problem.

Your vet noticed that your dog bled excessively after a simple surgical procedure (like tail docking, dew claw removal, or tattooing).

Your dog is experiencing unexplained bleeding episodes (like nose bleeds-epistaxis).

You and your veterinarian are anticipating surgery in a dog whose bloodline has experienced this form of hemophilia and want to be sure it is safe to proceed.

Even in pets that are documented vWD bleeders, estimates of the severity of the problem can vary from test to test on the same dog.

Stressful situations, infections, the phase of the pet’s heat cycle, and concurrent endocrine gland disease can all affect test results.

Complementary Tests :

CBC/WBC and blood chemistry profile including thrombocyte count, Clotting time determination, coagulation profiles (PT, APTT, and fibrinogen)

.................... DxMe