April 1, 2016 – A complete blood count is one part of the blood work included in your dog’s Golden Retriever Lifetime Study annual study examination and also if your dog gets sick. What does the CBC tell your veterinarian about your dog? At the simplest level, the CBC shows how many red blood cells (cells that carry oxygen from lungs to tissues), white blood cells (cells responsible for fighting infection), and platelets (cells that help form blood clots) are circulating in your dog’s blood at the time of measurement, but we can get more detailed information from this series of tests.
Let’s start with tests that relate to red blood cells:
- Red blood cells: RBC is a reflection of the number of cells circulating. If it is low, it indicates that your dog has anemia and, depending on the situation, additional diagnostics may be needed to find out why. If this number is too high, it usually indicates that your dog is dehydrated, although there are rare diseases that can cause a high red cell count in the absence of dehydration.
- Hemoglobin: HGB is the protein molecule inside red blood cells that carries (or binds) oxygen and carbon dioxide. Depending on where you live, hemoglobin levels will vary. The higher the altitude, the higher the hemoglobin level. Low hemoglobin levels also indicate anemia.
- Hematocrit: this reflects what percent of your dog’s total blood volume is taken up by red blood cells. It is another indicator of anemia and dehydration. This test is often a go-to in emergency situations because it is easy and fast to run in the clinic and can quickly tell us a lot about the health of your dog.
- Mean corpuscular volume: the MCV tells us the size of your dog’s red blood cells. It is useful because younger red blood cells are larger than mature red cells. If this number is high, it indicates red cells are turning over faster than expected. This can be due to bleeding or certain types of anemia.
- Mean corpuscular hemoglobin concentration: MCHC is calculated from the hemoglobin and hematocrit numbers, and tells average concentration of hemoglobin per red blood cell. It’s a tool used to determine what kind of anemia might be present.
Turning to white blood cells, or leukocytes, the differential count identifies what types of leukocytes are present, which gives your veterinarian an indication of the source of any inflammation. In the differential count, we get two measures for each cell type – a percentage and an absolute count. Percentages indicate if the ratio of different cell types is normal. Absolute counts indicate the degree to which each cell count is too high or too low. Typically, white blood cells are elevated when infection is present and can be decreased in certain disease processes or when some drugs are given, like chemotherapeutic agents. Specific types of cells are:
- Granulocytes belong to the branch of the immune system called the innate system. The innate system is in place and ready to respond to infection, but isn’t very sophisticated in its approach (like a sledge hammer).
- Neutrophils: these cells are the most common type of granulocyte and are elevated when infection is present. Their job is to go to the site of infection and kill everything in their path. In addition, they secrete proteins called cytokines to attract other components of the immune system.
- Band cells: these immature neutrophils, when their levels are elevated, indicate there is infection severe enough to quickly deplete mature neutrophils and the bone marrow is sending out young cells to replace the loss.
- Eosinophils: these cells typically are elevated when an internal parasitic infection is present (such as heartworms). They also are elevated in pathological immune responses such as asthma and allergic reactions.
- Basophils: these are the rarest type of granulocyte and usually are associated with ectoparasitic infections (such as mites or lice). They contain histamine, which is part of the allergic process.
- Monocytes also are part of the innate immune system. They go to sites of infection to kill pathogens, present antigens to lymphocytes (part of the immune system’s learning process), and produce cytokines (chemicals that attract the rest of the immune system). Once at a site of infection, they differentiate into one of two kinds of cells: macrophages (“big eaters”) and dendritic cells (cells with feet). Monocytes are elevated in many conditions, including infection, stress, some hormonal disease processes, and immune-mediated diseases.
- Lymphocytes are part of the ‘learned’ immune system because they generate antibodies in response to previous exposure, either through natural infection or vaccination. Lymphocytes are much more specific than the cells discussed above, but they also are slower to respond to infection. They can be elevated when certain types of infection are present and also with certain types of cancer. When they are low, it may indicate a disease process that is causing immune compromise.
Finally, we have platelets:
- Platelets are cells involved in causing blood to clot following injury. Low platelet counts may indicate certain autoimmune diseases or fulminant systemic disease.
Following each study examination, laboratory results are shared with participating veterinarians online at caninelifetimehealth.org under the “Lab Results” tab of the patient’s record. All lab results are interpreted by your veterinarian in the context of your dog’s clinical signs and symptoms. If you are concerned or have questions about your dog’s results, please talk with your veterinarian
