There are countless laboratory diagnostic tests for dogs. Some are chosen for routine monitoring, while others are elected for evaluation of specific diseases. Knowing which ones to order and how to interpret them takes years of training and experience. The purpose of this article is to familiarize the average pet owner to the tests routinely ordered. What is your veterinarian looking for, and what is the significance of the results?
Understanding Laboratory Diagnostic Tests For Dogs
Lets start with the minimum database. This is a set of tests that gives a snapshot of how the body is functioning overall. It is called the minimum database because it is the bare minimum combination of tests that yields the most comprehensive information about what is going on in the body.
It can be run at annual wellness exams to make sure everything is working appropriately and establish a baseline of the individual’s normal values. It can also be recommended in times of disease, to either identify an organ or body system that may be causing the issue. Sometimes it is all the information that is needed to make a diagnosis and treatment plan, while other times it can be consistent with or suspicious for a disease, but further testing is needed to make a definitive diagnosis. A minimum database consists of a complete blood count (CBC), biochemistry panel, and a urinalysis (UA).
A complete blood count is mostly looking at three components: red blood cells (RBCs), white blood cells (WBCs) and platelets. RBCs are the oxygen carrying cells. Elevated values may indicate dehydration or excitement, while decreased values indicate anemia. Anemia can then be categorized as blood loss, RBC destruction, or anemia of chronic disease. The rest of the CBC, the biochemistry, UA, physical exam, and sometimes additional tests are used to determine which type of anemia is present.
WBCs represent the immune system of the body. When WBCs are high, that suggests a systemic, or body wide, inflammatory response. That can occur with infection, auto-immune disorders, some cancers, and sometimes idiopathic, or unknown. Low WBCs can indicate prolonged infection (the body used them all up trying to fight the infection) or disease of the bone marrow.
Platelets are used for clotting. Having too many platelets circulating may be consistent with infection or bone marrow disease, and too few can be a sign of bleeding disorders.
The biochemistry panel includes blood sugar, liver and kidney values, proteins, and macrominerals (calcium, phosphorous, magnesium, potassium, chloride, and sodium). Deviations from normal blood sugar can indicate juvenile low blood sugar, potential liver shunt, some toxins or even cancer, sepsis, or diabetes, and sometimes just stress.
Kidney values can be elevated from kidney disease, urinary obstruction (can’t pee), or even dehydration. This is one reason why running this test with a UA is so important; the UA is what helps distinguish between the different causes of elevated kidney values. Liver values can be elevated due to trauma, degenerative changes, toxic insult, infection, or cancer. Sometimes more information is needed to pinpoint the cause, such as additional blood tests, imaging (ultrasound), or taking samples of the liver itself. Another cause for elevated liver enzymes is pancreatitis—sometimes when the neighboring pancreas is inflamed, the liver values go up as the digestive enzymes of the pancreas start irritating the liver.
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Additionally Cushing’s Disease, an endocrine disorder, may cause an elevation in at least one of the liver values, which when present, can warrant further testing when clinical signs are seen. The macrominerals help determine hydration status, acid-base status, and can be consistent with malnourishment, kidney or urinary diseases or endocrine diseases. Abnormalities in protein levels may indicate systemic inflammation, liver disease, blood loss, or malnourishment.
A urinalysis provides a wealth of information. It includes measurements of urinary pH, sugar, protein, RBCs, WBCs, bacteria, crystals, or sloughed cells from higher up the urinary tract. It may also show sperm in intact male dogs. The concentration of the urine helps determine how well the kidneys are working. A UA can reveal abnormalities such as urinary tract infections, urinary stones, diabetes, kidney failure, and many others.
A fecal exam is another routine test typically recommended for all puppies, and dogs with diarrhea. It is used to look for gastrointestinal parasites, such as roundworms, hookworms, and Giardia to name a few. Knowing which parasite(s) is/are present helps determine which medication would be most effective. Some parasites can not only make the pet sick, but can be transferred to other pets and people, so this is a very important test.
Heartworm tests are routinely recommended once a year for dogs on consistent prevention, but may be indicated more frequently when dogs are not on regular preventions. Heartworms are transmitted by mosquitos and live in the great vessels of the heart and lungs. They can be detrimental to the function of the heart and lungs and have serious consequences. Interestingly it takes six months from the time the dog is bitten by an infected mosquito to show up positive on the test. Heartworm tests are often accompanied by a tick-borne disease panel.
A tick-borne disease panel may include Lyme, Ehrlichia, and Anaplasma. Positives represent exposure to the agents, not necessarily disease. Presents of clinical signs and further testing may be needed to confirm.
Thyroid tests are fairly commonly run as well. A thyroid hormone called T4 may be part of a senior wellness panel or specifically when a veterinarian is suspecting thyroid disease. Dogs are way more likely to develop hypothyroidism (under active thyroid) than hyperthyroidism (overactive). The down side is this value may be influenced by other disease processes, and a low value by itself is not definitive for hypothyroidism. If a low value is identified, another, more specific thyroid hormone may be measured to confirm or rule out the presence of true hypothyroidism.
This just scratched the surface of the diagnostic tests for dogs available in veterinary medicine, but those mentioned are the ones dog owners are most likely to encounter. It is important to note that negative or normal test results are just as valuable as positives. Knowing what diseases are not present is important and decreases the use of unnecessary medications or procedures. Normal results may also indicate the curing or remission of some diseases.
Dr. Eric Weiner is a small animal veterinarian practicing in Orlando, Florida. He is a third generation veterinarian as both his father and grandfather are vets. Although he grew up following both of them around and wanted to be a veterinarian himself, he took a bit of a detour and attended Hofstra University originally as a music major.