You may have heard your veterinarian recommend bloodwork for your four-legged family member during one of your visits. There are a lot of reasons why your veterinarian may have thought this was important. It is also good to know that not all bloodwork is the same. There are literally thousands of different combinations that can be run at the lab or in the hospital. So, when we talk about bloodwork, what does that actually mean, and why is it so critical for our dogs and cats? This information will help us break down what you really need to know to ensure your dog or cat gets the care they need.
Why should we run bloodwork?
While it is far more common to think of bloodwork when a pet is sick, it is becoming the standard of care in veterinary medicine to run annual screening bloodwork on every pet, and for great reason. It allows us to monitor what is happening internally and actually get out in front of a disease. This is more than just the heartworm and fecal tests that most pets are already getting. Which panel is run is going to depend on how old the pet is, its breed and what species it is. For example, for a 2 year old dog, we often will not recommend annual screening that looks for thyroid disease since it is so unlikely at that age. We would, however, recommend this for a 9 year old dog. We go into a bit more detail later in this post, but this screening bloodwork serves two very specific purposes:
- It serves as a baseline for your individual pet. While we have a lot of data to help us determine what changes are normal and what are not in our bloodwork, each pet can have trends that are unique to them and them alone. By running annual screening bloodwork when your pet is totally healthy, it will be very obvious what changes are significant when your pet is sick.
- It also helps us monitor changes happening gradually, or catch a disease before your pet becomes seriously ill. For example, the BUN, Creatinine and SDMA increasing can help us see early kidney disease. With these tests, trends are as important as absolute numbers. If these values are trending up, even if they are in the “normal range”, we have enough evidence to say that there are changes happening in an animal’s kidney. This allow us to get a diagnosis and treatment started early, possibly extending a pet’s life by several years. If we had waited for a pet to become ill before we made the diagnosis, a lot more damage would have been done and more advanced treatment like hospitalization might be needed.
As you can see, annual blood screening, even in healthy patients, helps our veterinarians identify disease processes much earlier. We are lucky to live in a time when routine testing can pick up on issues before our pets even show symptoms. Early diagnosis is an important step to successful treatment. There are many diseases that would have been untreatable many years ago that we can now manage because we find them so much earlier. Our goal as a veterinary hospital is always to help your pets live the longest, healthiest and happiest lives possible, and routine annual blood work is closely associated with that mission.
Traditionally, illness(with clinical symptoms) has been the reason that bloodwork was recommended. When a pet becomes ill, bloodwork can offer a potentially life-saving view of what is happening internally. Our doctors will use the pet’s history and the physical exam findings to help guide what type of bloodwork is done, but here are a list of common diseases we are looking for with bloodwork:
- Kidney Disease
- Liver Disease
- Heart Disease
- Thyroid Disease
- Cushing’s Disease
- Addison’s Disease
- Viral, Fungal, Bacterial and Parasite Infections
- Immune Mediated Disease
Most veterinarians should be recommending some form of blood screening prior to surgery. This is an important step in the pre-surgical process because anesthetic drugs are often metabolized and excreted in the liver and kidneys respectively. If those organs are not working properly there could be serious complications during anesthesia. Anesthesia can also alter things like blood pressure, heart rate and the ability for a pet to move oxygen to important areas of the body. Because changes to red blood cells, protein levels and electrolytes can also put the same limitations on the body, it is imperative to check these values as well.
However, pre-surgical bloodwork can and should look different from one patient or surgery to the next. For example, it is common practice in our hospital to evaluate a pet’s ability to form blood clots prior to major abdominal surgeries like spays or a spleen removal. The reason behind this extra test is that we are working with very delicate blood vessels during these types of surgeries. If a pet is not able to form blood clots normally, they may have life-threatening bleeding even if the surgery is done properly.
What types of blood tests are there?
Chemistry Panel: You may hear veterinarians refer to this a “chemistry” or a “chem”. A chemistry panel looks specifically at non-cell parts of the blood such as:
- Protein levels
Because these can range from very small (testing 4-5 things) to very large (testing 25-27 things), there is a lot of variability in what these chemistry panels actually evaluate. There are even some differences from one laboratory to the next in what can be included in a chemistry panel. Most chemistry panels include at least some markers for the liver and kidneys as well as protein measurements.
More often than not, when a chemistry panel is run, it does not tell you the exact disease process that is going on, but it can vastly narrow down the search. For example, if the ALT, ALKP and GGT are all higher than expected, your veterinarian is going to tell you that there is a disease process occurring in the liver. It may take more tests or a further look into your pet’s history to say whether this is infection, toxin exposure, gall stones or another cause, but at least initial supportive care and treatment can be applied that will protect the liver as much as possible. These results help veterinarians create direct path that can be taken to getting a pet feeling better faster.
CBC: A Complete Blood Count is more frequently called a CBC or “Blood Cell Count” by veterinarians. A CBC measure multiple aspects of the cells that are in the blood. The data that is generated includes, not just total number, but also size, shape and diversity of blood cells. These cells include:
- Red blood cells
- White blood cells
There is still some variability from one CBC to the next as far as how many measurements that get taken on each individual type of cell, but these are much more uniform than the chemistry panels. By knowing what is happening with our red and white blood cells, a veterinarian can begin to speculate what is happening internally. As our doctors examine this part of the bloodwork, they are asking themselves several questions. Is there evidence infection (increases in some white blood cells)? Is this pet’s bone marrow working appropriately (decreases in some cell numbers without changes in size)? Are we worried about internal bleeding (decreases in red blood cells with some change in size)?
One thing that should always be coupled with a CBC is a blood smear. This is where a small drop of blood is placed on a glass slide, stained and examined under a microscope by a veterinary professional. The reason that this test is important is that while the actual numbers of red and white blood cells can all be normal, the cells themselves may not be developing normally or may have changes to them that point to one or two diseases in particular. In some cases, this visual examination of the blood can also help us see blood-borne parasites.
Other Types of Testing:
Urinalysis: This is a test that is actually run on urine rather than blood, but we include it in this discussion because a very large number of blood profiles include a urinalysis. The reason that these tests are often run with a blood profile are beyond the scope of this post, but in brief, the results help our veterinarians interpret other blood results more clearly. A fairly standard urinalysis includes applying urine to a test strip to evaluate markers like how acidic or basic the urine is (pH) or whether or not glucose (sugar) is present in the sample like what would happen in a diabetic patient. A sample of the urine should also be evaluated under a microscope to look for red or white blood cells, bacteria, crystals (microscopic mineral structures), or cells from the kidneys or bladder themselves. Finally, a standard urinalysis should also look at how concentrated the urine sample is. This may help us determine how hydrated a patient is or how well the kidneys are doing their job.
When done correctly and coupled with blood tests, a urinalysis can give us a lot of insight in to what is happening in our patients. For example, if a patient has a high blood glucose and has glucose in their urine, we are going to worry that they are becoming diabetic.
Heartworm and Fecal Tests: We mention these tests here because often a heartworm test, FIV/FELV test or fecal test is confused with some of other blood profiles we have already discussed. While the heartworm and FIV/FELV do technically require a blood sample, they are highly focused tests looking at just 1-2 disease processes. Heartworm and fecal testing are done every 6-12 months, and FIV/FELV tests are done 1-2 times as kittens, or if there has been a recent risk of exposure to these diseases. However, not all heartworm or fecal tests are the same, so be sure to speak with your veterinarian about how these tests are being run as well. For example, some heartworm tests also screen for a few tick diseases. The type of testing method for fecal testing may greatly change the accuracy of the results.
Individual Tests: While we wish there was one blood-profile we could run that would test for absolutely every possible ailment, unfortunately this does not exist. There are literally hundreds of individual tests that can be run solo or added to larger chemistry or CBC panels. Depending on what your pet is experiencing, your veterinarian may recommend adding these tests on to a larger profile or running them by themselves. It would be an ambitious task to discuss all of the additional tests here, but we have listed some of the most common ones.
-Thyroid Testing: There are a handful of markers that look at if body is producing too much or too little of the thyroid hormone.
-ACTH Stimulation Test/Dexamethasone Suppression Test: These tests measure if the body is producing too much or too little cortisol (Cushing’s and Addison’s Disease respectively). The method of collection for these profiles is unique in that a pet often has to have multiple blood samples taken over a period of several hours in the hospital.
-Gastrointestinal Profiles: This often includes a handful of values that look for diseases affecting the small intestines and pancreas. A pet should always be fasted before this test.
-Cultures: Cultures involve taking a sample from the body and seeing what, if any, bacterial or fungal organisms grow. This can be done with organisms living on the skin, in blood, urine, the lungs and many other areas of the body.
-PCR Testing: This is a highly specialized type of test that can detect tiny pieces of bacteria, fungi or viruses. It can be run on blood as well as other tissue types.
-Antibody Testing: This is a specialized blood test that looks for antibodies. Antibodies are produced to fight disease. By looking for antibodies against specific diseases, we can tell if a pet has been exposed to or is sick from that disease.
Outside laboratory vs In-House Testing
Another common question that concerned pet owners ask is why it may take a couple days to get blood work results back. Like many human medical professionals, our team prefers to send most of our blood testing to an outside laboratory. The equipment that they have available at these labs are slightly more accurate than what is available to in house use. Additionally, they have the ability to add on additional tests or specific procedures in real time to any result that seems abnormal. In many instances these tests are only available from the lab company and cannot be completed in a hospital setting. The laboratory runs hundreds of tests of a day and maintains strict quality control. They also employ a team of blood work specialist doctors that our team can consult with should there is an uncommon result. Samples are generally picked up from our hospital and results are back in 24-72 hours depending on the test. Some highly specific tests do take longer.
In-house testing is valuable in emergency situation, and our hospital is equipped with a full suite of advanced blood work machines. These in house machines can also be used if a patient needs surgery the same day as their blood test. We can have these results back in 15-30 minutes.
We hope you can see that “blood work” is not a general term that describes all blood testing. Our veterinarians recommend certain type of blood profiles for very specific situations. Those blood profiles are designed to give them important diagnostic information based on your pet’s species, breed, age, lifestyle, and condition. Most importantly, you should know that our veterinarians are committed to help your pets live long healthy lives. Every recommendation they make is based on the premise that we treat each and every one of our patients as if they are our own pets. We believe the information we get from these lab tests is important for our pet’s health and we wouldn’t think of treating your family any different.