What is a CBC?

Blog by Dr. Cindy Carter, DVM

A Complete Blood Count, or CBC, is a measurement of red and white blood cells in your pet’s circulation which gives us information about disease processes such as anemia, infection, dehydration, and cancer. We may recommend this blood test if your pet is sick, as a pre-operative assessment of health before placing your pet under anesthesia, or in routine senior wellness check-ups. Here is a quick overview of what we are looking at and why it is important.

Red Blood Cells

Red blood cells, or RBCs, are most important as carriers of oxygen throughout the body. We see their numbers reflected on your pet’s labwork as the PCV, or packed cell volume, and HCT, or hematocrit. If red blood cell levels are decreased in circulation, we call this anemia, and your pet may experience weakness, pale gums, or no symptoms noticeable to you at all. Some causes of anemia included both intestinal parasites
(i.e. hookworms!) and ectoparasites such as fleas, immune-mediated disorders, some toxins such as rat poison
, blood loss from trauma or internal bleeding disorders, kidney disease or any chronic disease process. An increase in the PCV/HCT often signals dehydration as there are more solid particles (the red blood cells) in the body in relation to the liquid portion of the blood (plasma).

White Blood Cells

There are five different types of white blood cells which are important to us: Neutrophils, Lymphocytes, Monocytes, Eosinophils, and Basophils.

Neutrophils are often seen in increased numbers with general infection or inflammation in the body. We may see bacteria within these cells as they “eat” the invaders within the bloodstream. Lymphocytes are, as their name implies, related more closely to the lymphatic system and decreases often indicate autoimmune processes or bone marrow issues while elevations are seen with viruses or lymphoma. When we see elevations in eosinophils, we often suspect allergies or parasitic infection. Monocytes may be increased with chronic infections, such as fungal disease. Basophils get somewhat left out and not paid much attention to since they aren’t a common concern (womp-womp!).

Platelets

Finally, in addition to red and white blood cells, we use the CBC to monitor platelets as well. Platelets play a vital role in clotting within the body. When they are decreased, it may be a sign of a virus, tick-borne disease, sepsis (bacterial infection within the bloodstream), or as a result of chemotherapy.

In addition to the CBC which is run by a machine, we often look at a blood smear on a slide under a microscope to directly see and count the red and white blood cells and platelets in the body. This is a great way to identify blood parasites, abnormal cells, and to verify that our automated counts were correct.

The Complete Blood Count is a window into your pet’s overall health, but it’s not the complete picture. We may recommend a Chemistry Panel in addition to look more specifically at the organ functions within your pet’s body. Stick around and I’ll blog about that next time! 🙂

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