D120
Complete Blood Count (CBC)

Description: Blood is collected from an animal and placed into a tube which contains material that stops clots from forming. The blood cells themselves are then analyzed according to their shape, size, color, and relative numbers present in the bloodstream (hence the term "count").

Diagnostic Value: High. Certain diseases can be detected and even initially diagnosed with a simple CBC. Problems such as anemia, severe infections, and some types of cancers can be detected.

Risks to Patient: Very low, provided that the blood is collected under sterile conditions by a trained professional.

Relative Cost: Low.

Normal Ranges: The following chart lists the normal ranges for many of the common items found on a CBC:

TEST
RANGES
UNITS
PCV
25-45
%
RBC
5-11
x 106/uL
Reticulocytes
0-50,000
#/uL
Platelets
200-800
x 103/uL
Segmented Neutrophils
2.5-11.5
x 103/uL
Band Cells
0-0.3
x 103/uL
Lymphocytes
1.5-7.0
x 103/uL
Eosinophils
0-1.5
x 103/uL

Interpretation of Results:
  1. Packed Cell Volume (PCV) - This is the total percentage of the blood that is composed of red blood cells.
  1. A high PCV occurs most commonly with dehydration, hyperthyroidism, and certain heart defects.
  2. A low PCV can be the result of not enough red blood cells (anemia), or the occasional state of over-hydration. There are many different causes for anemia (see B below).
  1. Red Blood Cell (RBC) - This is the total number of red blood cells in one microliter of blood.
  1. Low numbers of RBCs (anemia) can be the result of blood loss, inadequate RBC production in the bone marrow, or actual destruction of the RBCs within the body.
  1. Reticulocytes - Reticulocytes are immature red blood cells. This value is usually measured only in cases of anemia.
  1. High numbers of reticulocytes indicate a regenerative response (i.e. the bone marrow is producing more red blood cells).
  2. When low numbers of reticulocytes occur and anemia is present, there is usually a problem with production of red blood cells (i.e. bone marrow malfunction).
  1. Platelets - Platelets are circulating compounds that help blood to clot.
  1. If low platelet numbers occur, the animal may be prone to bleeding disorders. Low platelet numbers can be due to certain infections, some types of cancer, autoimmune disorders, and as a side effect of some drugs.
  1. Neutrophils - These are white blood cells (WBC) that are important in fighting infection.
  1. High numbers of neutrophils (neutrophilia) occur when there is an infection, the animal is stressed (coming to the clinic), or when steroids have been administered.
  2. Low neutrophil numbers (neutropenia) can occur with very severe bacterial infections, some viral infections, and when there has been long term bone marrow damage.
  1. Band Cells - Band Cells are the early stages of a neutrophil.
  1. The presence of band cells usually indicates that an infection is occurring in the body. When high numbers of band cells are observed, it is called a "left shift."
  1. Lymphocytes - These are WBC that are part of the body’s immune system.
  1. High levels of lymphocytes (lymphocytosis) can occur when the animal is excited or if there is a cancer of the bone marrow, such as leukemia.
  2. Low lymphocyte numbers (lymphopenia) indicate administration or release of steroids, viral infections, or stress.
  1. Eosinophils - These are white blood cells that are common in situations where irritation or inflammation of tissue is found.
  1. High numbers of eosinophils indicate a possible parasite problem, allergic reaction, or certain cancers.

This section lists only a few of the most common possibilities for cell changes in a CBC. A physical examination, additional history, and other tests may be required before a specific diagnosis can be determined.