The Facts About Dog Cancer Screening Tests

The Internet is buzzing with talk about the VDI-TKcanine+ cancer test for dogs. Manufactured by the Veterinary Diagnostics Institute (VDI), this dog cancer screening test made news after it was given the “Seal of Excellence” by the National Canine Cancer Foundation, which recently formed an exclusive partnership with VDI.

According to the National Canine Cancer Foundation, the VDI-TKcanine+ cancer test will “help aid diagnosis when cancer is suspected, and to monitor the course of treatment once the presence of cancer is confirmed. VDI-TKcanine+ is a test run by veterinarians and is made available to all veterinarians in the U.S.”

VDI currently has two tests for dogs available: VDI-TKcanine+ and INCase. Both tests screen for cancer by looking for two biomarkers that are elevated in patients with cancer; C reactive protein and thymidine kinase.

VDI’s INCase test is being marketed as a screening test for dogs with no clinical signs or findings of cancer, however the company is unsure about how many different types of cancer it will detect.

Dog Cancer Tests Better But Not Perfect

Blood tests to monitor dog cancer have been in use for a few years, like the OncoPet RECAF test. The availability of more cancer tests is exciting news, so does this men that screening for canine cancer in our healthy dog or cat is as easy as asking our vet to take a blood sample?

We asked Dr. Avenelle Turner, DVM, Diplomate ACVIM (Oncology), of Southern California’s Veterinary Cancer Group, to share her thoughts about this newest dog cancer blood test, VDI-TKcanine+.

“I think it is one of the better tests out there if used correctly,” says Dr. Turner. However, she cautions that pet parents must first keep in mind that the VDI-TKcanine+ test has only been validated for dogs with lymphoma or hemangiosarcoma; it is not a screening test to be used when cancer is not suspected.

Dr. Turner says she has used the VDI-TKcanine+ test to help monitor the remission status of her patients with lymphoma. However, she advises pet parents to remember that oftentimes canine cancer blood tests still have a high number of false positives, which doesn’t make them an ideal diagnostic tool for confirming the presence of cancer in an otherwise healthy dog.

How the VDI-TKcanine+ Test Works

The VDI-TKcanine+ test can be used in the following situations:

• When a dog is suspected of having lymphoma or hemangiosarcoma: a high positive test result is suggestive of lymphoma/hemangiosarcoma 85% of the time and if the test is negative, there is only a 4% chance that this test would not detect either disease.
• When a dog has a confirmed case of lymphoma: the value of the test also indicates the amount of disease. For example, the higher the number, the more “tumor burden.”
• When monitoring response to treatment; the values will get lower as more cancer is killed, higher if the therapy isn’t working. If this test is done at the initial diagnosis of lymphoma prior to therapy, values lower than 30U/L show a positive prognostic indicator and are suggestive of a longer survival with treatment. A test value of 100U/L or higher is a negative prognostic finding and is suggestive of a shorter survival even with treatment.

The Downside of Higher Sensitivity Tests

VDI reports that their INCase test has an overall 99% sensitivity, which means that if you have a negative test result, there is less than a 1% chance that the dog has cancer. And while this test is well-regarded in the veterinary community because of its high sensitivity, the irony is that “the more sensitive a test is, the more false positives you will have,” according to Dr. Turner. With the INCASE test, about 10-15% of dogs will test positive but not actually have cancer.

False positives also happen when a dog has inflammation anywhere in the body. For example if a dog has bad skin, itchy ears or irritable bowel disorder (which all cause inflammation in the body), the false positive readings can soar as high as 50 percent.

Since most dogs have some inflammation somewhere in their body, up to half of all dogs tested may undergo costly cancer staging diagnostic tests, only to reveal that there was no cancer in the first place.

Dr. Jennifer Coats, author of the PetMD blog Fully Vetted, stated in her blog that she believes that the current canine cancer screening test technologies still have a long way to go.

“The blood tests have a relatively high rate of false positive results, which means that a large number of clients will be told that their pets might have cancer when they really do not. This will bring about a lot of unnecessary worry and will necessitate additional, expensive diagnostic testing before coming to a definitive diagnosis of “no cancer.”

Accurate Dog Cancer Testing Closer Than Ever

When the Texas A&M Veterinary Oncology Clinic was asked about this new test and blood screening tests in general, a clinic spokesperson on Facebook said “we are still researching their efficacy. It is still too early for us to say whether or not we’d recommend them to our clients, but we’ll let everyone know what our research concludes!”

Opinions given by veterinary professionals indicate that checking for canine cancer still isn’t as easy as having our vet draw a blood sample during our dog’s annual check-up, but thanks to the ongoing development of better tests like the VDI-TKcanine+, we’re closer than ever to detecting dog cancer in its earliest stages.

Recommended Reading:

PetMD, Fully Vetted Blog: Blood Tests for Cancer Screening?
Healthy Pets; Mercola: New Simple Blood Test Can Detect Cancer in ‘Man’s Best Friend’…
National Canine Cancer Foundation: Blood Test For Canine Cancer