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Can a Blood Test Show Cancer in a Cat?

cat blood test

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Dr. Lorna Whittemore Photo

Reviewed & Fact-Checked By

Dr. Lorna Whittemore

Veterinarian, MRCVS

The information is current and up-to-date in accordance with the latest veterinarian research.

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As pet owners, it’s our responsibility to ensure that our pets live healthy and happy lives while they’re under our care. Sometimes, we can do clear-cut things such as manage our pets’ diet and provide plenty of exercise and play opportunities. However, there are instances where there’s a lack of clarity and or easy path to resolving health issues.

Cancer is one of these illnesses that can be difficult to detect, even with thorough blood tests. While one in five cats will be diagnosed with cancer1, it’s a disease that can remain well hidden for a time. Cats are also known to instinctually hide their pain2, so it can be challenging to know for sure if a cat has cancer until the later stages.

A blood test may show signs to be suspicious of some cancers, but it doesn’t provide a comprehensive diagnosis or understanding of all cancers. Most cancers do not have a specific blood test to check for them. Here’s what we know so far about blood tests and how veterinarians can currently detect cancer in cats.


Some Blood Tests Can Detect Some Cancers

Most types of cancer cannot be found through blood tests alone. However, some tests may be able to help narrow down a diagnosis. Some cancerous tumors will affect the organ they are growing in or cause paraneoplastic syndromes resulting in changes when examining a blood sample. Blood samples can be run to look at enzyme markers for organs and blood cell counts.  They can also be assessed under the microscope to look for changes in cell shapes.

Blood work can increase the suspicion of cancer through white blood cell counts for instance. Leukemia is a group of cancers that alter the number of white blood cells in the bloodstream. So, if a cat’s lab results show significant alterations in white blood cells, it could be a marker for leukemia. However infections and parasites amongst other things can also cause changes.

Anemia is a reduction in the number of circulating red blood cells or reduction in their oxygen carrying ability and can have a number of causes. Some cancers result in anemia and it can flag that further investigation is needed.

Veterinarians may also do blood tests to examine thymidine kinase (TK) and C-reactive protein (CRP) serum levels. Elevated levels of TK and CRP can be linked to certain cancers but again not exclusively so need to be interpreted carefully.

Cats with feline leukemia virus and feline immunodeficiency virus are more likely to develop cancers and these viruses can be tested for with an in-clinic kit.

cat blood sample
Image Credit: SingingMedia, Shutterstock

Other Ways Veterinarians Diagnose Cancer in Cats

As we can see blood tests are useful in determining the overall health of a cat but not necessarily in detecting cancer. There are several other methods that veterinarians can use to diagnose cancer.

Firstly, they will take a thorough history from you the owner detailing any concerns you have or changes you have noted.  Next comes the physical examination to feel, look and listen for any abnormalities.  Checking temperatures and changes in weight are also helpful.

If a lump is found they may be able obtain a fine needle aspirate (FNA). This minimally invasive procedure can help provide more information on the mass and if it’s malignant or benign by drawing out a number of cells which can be examined under a microscope. FNA have limitations and at times a surgical biopsy may be needed.

Vets may need to then move on to other testing such as x-rays and ultrasound to assess the structures within the body.

A urinalysis can also point to certain types of cancers, such as transitional cell carcinoma (TCC) and the health of the urinary tract system.

Blood samples provide an insight into health and are important in cancer patients and those undergoing treatment.  But as of yet there is no blood test that can confirm or rule out all cancers.


Final Thoughts

When it comes to using blood tests to detect cancer in cats, veterinarians have to consider all the information as a whole. They usually have to combine a series of different types of tests to determine if a cat has developed cancer.

One of the best chances of catching cancer in the early phases is to be on top of getting your cat to the veterinarian’s office for routine checkups and monitoring for changes at home. Not only do these checkups look for any abnormalities, but they’ll also help your veterinarian to better understand your cat as an individual.

Featured Image Credit: PRESSLAB, Shutterstock

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