Understanding your pet's blood tests

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Analysis of blood samples can help determine the state of your pet's health and assist your vet in diagnosis of illness or injury. There are some blood tests that your vet may want to perform during your pet's regular checkups. Minimal risk is associated with performing the tests, and the information gained is invaluable.

When is blood testing used?

Blood testing is commonly used to help diagnose disease in animals. It can also help determine the state of your pet's health during regular check-ups. Although a complete blood count (CBC) or a chemistry profile can be performed separately, these tests are frequently done at the same time. When the results are interpreted together, they provide a good overview of many of the body's functions. Your vet will combine this information with physical examination findings, medical history, and other information to assess your pet's health status and determine if additional testing should be recommended.

What do the tests measure?

Complete blood count

The CBC involves counting the numbers of different types of cells in the blood. This can be very useful in many ways, including identifying if the pet is dehydrated, anaemic (having inadequate numbers of red blood cells), or dealing with an infection. The CBC measures the numbers of different types of cells but an examination of a blood smear provides additional information about the form of the red blood cells, white blood cells, and platelets. The CBC results may list abbreviations for the various tests included in a CBC:

  • HCT is the hematocrit, which indicates how many red blood cells are present. A low HCT might indicate anaemia, and a high HCT could indicate dehydration.
  • Hgb is the quantity of haemoglobin within each red cell, which can help determine how well the red blood cells will carry oxygen to the body's tissues.
  • WBC is the total white blood cell count. Certain types of white blood cells may increase in number when there is infection or inflammation in the body. If the total number is low, it could mean several things, including a severe infection that has overwhelmed the body, or a bone marrow problem that is limiting production of white blood cells. There are several different types of white blood cells, which respond to different events in the body. EOS (eosinophils) are white blood cells that tend to increase in number when the body is dealing with an allergy or some parasites.
  • PLT is the quantity of platelets (also called the platelet count). Platelets are involved in the body's blood clotting process.

Chemistry Profile

The chemistry profile measures a variety of chemicals and enzymes (proteins that are involved in the body's chemical reactions) in the blood to provide very general information about the status of organ health and function, especially of the liver, kidneys, and pancreas. The chemistry profile also shows the patient's blood sugar level and the quantities of important electrolytes (molecules like sodium, calcium, and potassium) in the blood.

Chemistry values that help provide information about the liver include ALKP (alkaline phosphatase), ALT (alanine aminotransferase), AST (aspartate aminotransferase), and TBIL (total bilirubin).

Chemistry values that help evaluate the kidneys include the BUN (blood urea nitrogen) and CREA (creatinine). Of these two values, creatinine is a more sensitive indicator of kidney damage. There should be concern even if it's only slightly elevated.  

AMYL (amylase) and LIP (lipase) are enzymes produced by the pancreas.

How are blood tests performed?

To perform a CBC and chemistry profile, your vet must first obtain a small blood sample from your pet. This may take only a few seconds if the patient is well behaved. For patients that are very frightened or not well behaved, your vet may want to use a muzzle, towel, or other gentle restraint device. In some cases, such as in patients with very thick fur, it may be necessary to shave the hair from the area where blood will be drawn. This is often a good way to find the vein quickly, and the hair will grow back.

Some veterinary surgeries have in-house blood analysis equipment, so they can perform a CBC and chemistry profile in the practice and have results the same day. Other surgeries send blood samples to an external laboratory for these tests to be performed. If an external laboratory is used, results are generally available within 1 to 2 days.

Following a meal there are changes to a number of the constituents of blood and these may affect the results of a chemistry profile, your vet may recommend that your pet is fasted for 8 to 12 hours before blood is drawn. In most cases, water can still be offered. Please let your vet know if this temporary fast will be a problem for you or your pet.

You must also tell your vet about any medications or supplements that your pet is receiving, as some products can alter the results of a chemistry profile.

What are blood tests used for?

When a pet presents with clinical signs indicating an illness, a CBC and chemistry profile is often performed very early during the diagnostic process. Even if results of this initial testing are all "normal", this information can rule out a variety of medical conditions. If results of a CBC and chemistry profile are abnormal or inconclusive, your vet may recommend additional testing to get closer to a diagnosis.

A CBC and chemistry profile is also part of routine blood work that may be performed before a pet undergoes general anaesthesia for a surgical procedure. If test results are abnormal, your vet may recommend additional precautions to help ensure your pet's safety during the procedure. Your vet may also recommend postponing the procedure or choosing an alternative treatment option.

Depending on your pet's age and health history, additional tests (such as thyroid testing or urinalysis) may also be recommended as part of wellness testing. For elderly or chronically ill pets, your vet may recommend blood work more frequently. Wellness blood work screens for many medical conditions, including diabetes and kidney disease. In many cases, early diagnosis and management can improve quality of life and the long-term prognosis for pets with chronic illnesses.

Performing a CBC and chemistry panel poses minimal risk for your pet, and in many cases, the information your vet gains from this testing is invaluable.

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