Complete Blood Count (CBC)

The cellular components of blood are red blood cells, white blood cells, and platelets, all of which are suspended in the plasma. The complete blood count or CBC is a standard test to evaluate the status the cellular components of your blood. A CBC is routinely done during treatment -- especially prior to receiving any chemotherapy. The count is done with automated equipment. The CBC is also used to check for anemia, infection and other diseases.

Red Blood Cell Count (RBC) - The count of the number of red blood cells per unit volume of blood. Red blood cells (erythrocytes), are the most numerous of the three cellular components of blood and normally make up almost half of the blood's volume.

Hemoglobin(Hgb) indicates the amount of this oxygen-carrying protein within red blood cells. Hemoglobin enables the RBCs to carry oxygen from the lungs and deliver it to all body tissues. Oxygen is consumed to provide energy to cells, leaving carbon dioxide as a waste product, which the red blood cells carry away from the tissues and back to the lungs. Red blood cells usually flow smoothly through the blood vessels.

A low hemoglobin value is indicative of anemia. This may be the source of your fatigue or tired feeling. There are many causes of anemia, but with prostate cancer, it might be due to the cancer, chemotherapy treatments or hormone therapy.  It is always wise to check for iron deficiency anemia via a serum iron test and an total iron binding capacity(IBC or TIBC). Iron deficiency anemia is well discussed at www.nlm.nih.gov/medlineplus/ency/article/000584.htm. Another useful measurement is mean corpuscular volume (MCV). MCV is a measurement of the average size of your red blood cells (RBC). An elevated MCV occurs when your RBCs are larger than normal (macrocytic), for example in anemia caused by vitamin B₁₂ deficiency. A low MCV, indicates your RBCs are smaller than normal (microcytic), such as is seen in iron deficiency anemia.

The Hematocrit(Hct) measures the proportion of red blood cells to the total blood volume and is reported as a percentage.

What can I do if my RBC or Hgb are low? Epoetin Alfa(Procrit^® and Epogen^®) is sometimes administered by your oncologist as an aid to alleviating anemia. This is an intramuscular injection. Another drug used in the United States for low RBC is Aranesp^® (darbepoetin alfa) which has a longer half-life than epoetin alfa.

White blood cell count (WBC) - The number of white blood cells in a specified volume of blood. White blood cells form the mainstay of your immune system -- a low number might increase your risk of infection and a high number possibly indicating that you have an infection.  Some chemotherapies increase the risk of 'immunosuppression" so oncologists set a lower limit to protect you in the event this happens.

Differential white blood cell count - Percentages of the different types of white blood cells.  There are five main types of white blood cells: neutrophils (also called granulocytes - GR and GR# in the table below), lymphocytes, monocytes, eosinophils, and basophils.

White blood cells (leukocytes) are fewer in number than RBCs, with a ratio of about 1 white blood cell to every 660 red blood cells. White blood cells can adhere to and penetrate the sidewalls of blood vessels as they wander about ready to fight infections. There are five main types of white blood cells that work together to provide the body's major mechanisms for fighting infections, including the production of antibodies. Neutrophils, also called granulocytes because they contain enzyme-filled granules, are the most prevalent white blood cell type. They help protect the body against bacterial and fungal infections and ingest foreign debris. They consist of two types: band (immature) and segmented (mature) neutrophils.

Oncologists pay particular attention to the absolute neutrophil count (ANC)(which is also called the absolute granulocyte count or AGC or GR# as many of the cytotoxic chemotherapy drugs decrease the ANC, making patients more susceptible to infections. Most chemotherapy regimens require an absolute neutrophils count (GR and GR# in the table below) to be ≥ 1500 cells/μL.

Lymphocytes consist of two main types: T lymphocytes, which help protect against viral infections and can detect and destroy some cancer cells, and B lymphocytes, which develop into cells that produce antibodies (plasma cells). Monocytes ingest dead or damaged cells and provide immunologic defenses against many infective organisms. Eosinophils kill parasites, destroy cancer cells, and are involved in allergic responses. Basophils also participate in allergic responses.

What can I do if my WBC or GR# are low? This is called neutropenia. A low WBC can be treated with colony stimulating factors (CSF).  Examples of CSFs are G-CSF(granulocyte colony-stimulating factor) - Neupogen^® and GM-CSF(granulocyte macrophage colony-stimulating factor) - Leukine^®.  These subcutaneously injected drugs may increase the WBC/GR# enough that you can continue chemotherapy. Leukine is also sometimes given by I-V. Another possibility is that your next chemotherapy treatment will be delayed until your white blood cells recover.

Platelet count(Plt) - the number of platelets in a specified volume of blood.

Platelets (thrombocytes) are the 3rd cellular component of blood and are cell-like particles smaller than red or white blood cells. As part of the blood's protective mechanism for stopping bleeding, they gather at a bleeding site, where they are activated. Once activated, they become sticky and clump together to form a plug that helps seal the blood vessel and stop the bleeding. At the same time, they release substances that help promote clotting. The medline plus page at http://www.nlm.nih.gov/medlineplus/ency/article/003647.htm provides additional information and links.

Thrombocytopenia is defined as a low platelet count(below the lower limit of normal) and is called thrombocytopenia. Oncologists are reluctant to treat patients with chemotherapy when the platelet count falls below 100,000/μL, although treatment might be continued at lower values depending on the patient. The panic level is < 25,000/μL.

Less commonly used CBC values are described below the table.

Here is an example of a complete blood count panel for IMA Patient

1. The highlighted entries focus on some of the more key values.

2. Note that there are many ways of reporting these values depending on the units used. For example with platelets you might see any of these ways of reporting the test results:  thousands in a microliter of blood (150,000/µL or 150.0x10³/µL) or as millions in a liter of blood (150.0x10⁹/L).

Mean platelet volume (MPV) is a machine-calculated measurement of the average size of your platelets. New platelets are larger, and an increased MPV occurs when increased numbers of platelets are being produced. MPV gives your doctor information about platelet production in your bone marrow.

Mean corpuscular hemoglobin (MCH) is a calculation of the amount of oxygen-carrying hemoglobin inside your RBCs.

Mean corpuscular hemoglobin concentration (MCHC) is a calculation of the percentage of hemoglobin in the RBCs. Decreased values point to hypochromasia, decreased oxygen- carrying capacity because of decreased hemoglobin inside the cell. Hypochromasia is seen in iron deficiency anemia and in thalassemia.

Red cell distribution width (RDW) is a calculation of the variation in the size of your RBCs. This is useful in diagnosis of anemias such as pernicious anemia.

Low RBCs and Low WBCs(Neutropenia) - Blood Cell Formation

Chemotherapy can cause damage to other rapidly dividing cells while in the process of killing cancer cells.  Bone marrow is one such rapidly dividing cell that is responsible for producing red blood cells (RBCs), white blood cells (WBCs) and platelets. This reduced activity of the bone marrow is called myelosuppression.

White blood cells decrease most rapidly, because they have the shortest life span. Red blood cells and platelets will decrease less rapidly under the onslaught of chemotherapy.

Lymphocytes are a type of white blood cell and they are also produced in the lymph nodes and spleen.  The thymus gland, which is active only in children and young adults, also produces and matures T lymphocytes.

The speed of blood cell production is controlled by the body's need. When the oxygen content of body tissues or the number of red blood cells decreases, the kidneys(90%) and liver(10%) produce and release erythropoietin, a hormone that stimulates the bone marrow to produce more red blood cells. The bone marrow produces and releases more white blood cells in response to infections and more platelets in response to bleeding.

A single type of cell in the bone marrow, called a stem cell, is the origin of red blood cells, white blood cells and platelet cells. Stem cell division results in an immature red blood cell, white blood cell, or platelet-producing cell (megakaryocyte). Division of the immature cell results in further maturation giving rise eventually a red blood cell, white blood cells or platelets.

Author: Howard Hansen,  1/26/04