Understanding the Most Common Tests Performed by Veterinarians
By Cindy McGovern
I recently took my 11-year old, outwardly healthy cat in for her annual checkup and vaccinations. In addition to the normal physical exam, this visit included blood work and urinalysis. I’ve had the same vet for almost 20 years and I trust his judgment. But after seeing the $400 bill, I decided to learn more about the detailed laboratory tests that were done.
One reason these tests are done is because your pet can’t tell you how they feel and they can help identify conditions the physical exam can’t. The tests also establish a benchmark of health for the animal, which is particularly helpful as your pet ages. You can think about these tests as similar to the blood pressure measurements that are taken each time you visit the doctor.
By definition, a screening blood test is a test done to detect disease before its symptoms manifest. They are also important for animals of all ages who are undergoing surgery. A complete blood count, or CBC, is the most common blood test performed on pets and people, as it provides a window into your pet’s overall health. It gives information on hydration status, anemia, infection, the blood’s clotting ability, and the ability of the immune system to respond to infection. This test is essential for pets with fevers, vomiting, diarrhea, weakness, pale gums, or loss of appetite. If your pet needs surgery, a CBC can also detect some bleeding disorders or other unseen abnormalities that might impact their recovery.
The blood work may also include blood chemistries. These common blood serum tests evaluate organ function, electrolyte status, hormone levels and more. They are important in evaluating older pets; pets with vomiting, diarrhea or toxin exposure; pets receiving long-term medications; and pet health before anesthesia.
The following are the most common blood chemistry tests:
Blood urea nitrogen (BUN) and creatinine help indicate kidney health. While BUN can also be affected by hydration level and certain liver conditions, creatinine is a fairly specific indication of kidney function. Creatinine levels that fall outside the normal range can be an indication of kidney disease, infection, or failure.
ALT and bilirubin indicate liver health. When a liver is not functioning properly, these levels might increase. Noting changes in the levels of these chemicals in the blood over time will identify a liver problem.
Amylase and lipase are sometimes measured to indicate pancreatitis. However, these are not the most sensitive way to diagnose that condition, and animals with pancreatitis could have normal amylase and lipase levels.
Blood glucose levels are measured to diagnose diabetes mellitus, during which glucose is high. Your vet may measure blood glucose levels if you’ve noticed your pet drinking water, urinating or eating excessively. Low blood glucose levels can indicate liver failure from other causes.
Electrolyte, such as potassium, sodium, and chloride levels can be affected by a wide variety of illnesses and conditions, including dehydration, kidney failure, and Addison’s disease.
Thyroxine (T4) levels provide general information about thyroid condition. Thyroid disease is common in dogs and cats, especially older ones. Dogs usually have low thyroid issues while cats have increased thyroid hormone disease. Because thyroid disease can resemble other conditions, a separate thyroid test may be called for. Thyroid disease can usually be managed, but the sooner it’s caught and treated, the better.
A heartworm test identifies whether or not a dog is infected by heartworms. Heartworm disease is serious and can eventually cause death, so most veterinarians recommend testing yearly, even if the dog is on heartworm medication. The majority of the time, this test is done quickly in the veterinarian’s office by means of a SNAP test which looks for proteins from the parasite in the blood. Early detection of the disease is critical to the success of treatment.
Feline Leukemia (FeLV) and Feline Immunodeficiency Virus (FIV) are common tests for kittens and cats, especially those whose history isn’t well known. FIV is sometimes called feline “AIDS” because like HIV, it attacks the immune system and makes the cat vulnerable to infections. FeLV weakens the immune system, but also increases their risk of lymphosarcoma, a highly malignant cancer. FIV and FeLV are serious diseases, but they are not death sentences and cats can still live a good life with them.
Stool samples are used to screen for various parasites such as Giardia and Cryptosporidium. Giardia lives in your dog’s intestines and infects older dogs, but more frequently puppies. Dogs become infected when they swallow Giardia in water or other substances that’s been soiled with feces. Diarrhea is the most common symptom and long-term infection can cause weight loss, poor health and in severe cases, death. Cryptosporidiosis causes gastroenteritis and diarrhea, but is less common in dogs and cats than farm animals. It usually presents as diarrhea and can be severe in young or weak animals or those with a compromised immune system. The eggs of other parasites, such as roundworms, hookworms, and tapeworms, can be found in stool samples, as well as adult worms or tapeworm segments.
Testing a urine sample can help uncover infections, bladder stones and diabetes. These tests are important if your pet shows increased urine volume, increased drinking of water or frequent short urinations. Normal urine is typically yellow or amber in color and is usually transparent or clear. The presence of diseases or infections may change the color or clarity. A large number of red blood cells in urine usually indicates bleeding somewhere in the urinary tract, while large numbers of white blood cells can indicate infection. A large amount of bacteria may also indicate infection.
If you have questions or don’t understand the test being done, be sure to ask your vet. While no one wants to conduct unnecessary tests, they do help show the pet’s health and can detect diseases in the early stages. In my case, the patient is in excellent metabolic health.
Click to access diagnostic-testing-handout.pdf
About the Author: Cindy McGovern is a King Street Cats volunteer and supports two Siberian cats.