Blood Tests

By Dr. Moira Drosdovech

The why of blood tests isn’t terribly complicated. Following a really thorough physical exam, there may still be questions about the health of your pet. After all, they aren’t super communicative in ways we can always understand (begging might be fairly clear...) so they are rather unable to help much towards their diagnosis! With blood tests, veterinarians can “see” the inner workings of the pet’s organs and body parts more clearly.

We can get hints from our history taking and physical exams. Vets should ask a LOT of questions during the course of the appointment about your pet’s habits and changes that might have been observed. For instance, are they still eating and drinking the same as they always have or are they eating less and drinking more water? Maybe they are both eating more and drinking more! Are they losing weight? These are critical bits of info that make it much easier to come up with a plan. Another example is when your pet's skin and mucous membranes such as their gums are yellow-tinged, this can often point us towards something going on with the liver. Doing a blood panel will help guide our decision on what further tests are needed to aid in making an accurate diagnosis more quickly.

Some blood tests are done as a routine before an operation on an otherwise healthy pet just as in the human field primarily so veterinarians don't get any surprises during surgery or recovery. Very occasionally, some disorder is discovered that needs further attention before surgery is done. I will not soon forget a young Shih Tzu puppy from way back when I first started in 1987 that was in for a neuter and we did some blood work only to find out he was suffering a terminal case of congenital renal dysplasia (poorly formed kidneys that just sadly did not work well at all). Shortly after this diagnosis, the puppy had to be put to sleep as his kidneys were shutting down and I found this very distressing. There have been others of this nature, but this one was most memorable as it was the first for a young impressionable vet.

Other types of blood tests are done on perfectly healthy pets to get more information unrelated to illness. For example, I have done tons of vaccine titre testing in the last 2.5 decades to check the Distemper and Parvovirus immune status in dogs after their 4 month vaccine and over the next several years. This has enabled me to comfortably recommend to my dog owners that a booster is not needed the vast majority of the time. Breeders might want to do a nomograph on their females which is basically a titre test with a twist as it also

predicts at what age the puppies will need to have their first vaccine. Breeders are often interested in titres for certain bacteria such as Brucella that can wreak havoc in a breeding program or to rule out issues with immunerelated platelet diseases. If you want to move to Australia or New Zealand, your pet will need to get a vaccine for Rabies and this is followed by mandatory Rabies titre testing as some countries, like these two, have no Rabies cases at all and incoming pets must be tested to prove they are free from this virus.

Prior to surgery in a particularly vascular region such as the liver, it is prudent to know if the pet can clot in case of hemorrhage during or after surgery so a coagulation panel is needed. And should there be bleeding, blood typing of both donor and recipient is required before transfusion.

Some pets are on medications that require monitoring either of the drug levels themselves in the bloodstream to make sure they are at therapeutic levels (eg. Phenobarbitol for seizures) or of the molecule(s) that the drug is altering such as in Canine Cushing’s Disease or Hyperthyroidism in cats. These tests are primarily ordered to check on the effectiveness of the medication, but also to make sure it is not causing damage to the target organ. The same goes for Diabetes Mellitus which requires fairly regular monitoring of glucose levels to make sure the Insulin dose is just right.

Mostly we have been discussing chemistries which are basically the different molecules in the bloodstream released by the various organs or as breakdown products

of metabolism. What about the blood cells themselves? Why is it important to get information about these?

A Complete Blood count or CBC is a very commonly performed test that gleans a lot of information. This test is an actual count of the various types of blood cells in circulation such as red blood cells (RBCs), white blood cells (WBCs), and platelets and it also gives information on protein levels. These numbers give us a hint as to whether there is an active infection, autoimmune issues, leukemias, platelet abnormalities, tumours of some organs, the status of the bone marrow and more. RBC’s often become misshapen depending on disease processes and detecting these changes can help detect certain types of tumours or deficiencies.

A time we definitely want to run a CBC is if your pet’s gums are very pale as this could mean any one of a number of things such as internal bleeding from rat poison, autoimmune anemia, immune-mediated thrombocytopenia (platelets being destroyed), cancer of the bone marrow, other chronic diseases, some viral infections, and more, but something for sure is causing a low RBC count. Blood tests will narrow down which of the myriad of illnesses could be causing the paleness.

I really have barely touched on the different types and purposes of blood tests, but it is easy to see how important they can be for the health and longevity of your pet(s). The biggest issue with some pets is getting the blood out of them so practice various forms of restraint with them starting at an early age so they just think it is another one of those strange human hugs!

BLOOD TEST RESULTS

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