Knowing your CBCs

Knowing your CBCs

CBC - The Complete Blood Count (CBC) is one of the most common tests ordered by a provider. It is a routine test used to evaluate the blood and general health. A CBC measures all the following parameters: red blood cell count (RBC), white blood cell count (WBC), hemoglobin, hematocrit, three red cell indices, and the white cell differential. Platelet counts are usually included in a CBC.

RBC Count - The RBC count is the number of RBC's in a cubic millimeter of blood. The RBC's are the cells produced in the bone marrow that carry oxygen to your tissues. A slight decreased value is not cause for alarm. However, a markedly decreased value should be thoroughly investigated. A person with a significantly low RBC count can have symptoms of fatigue, shortness of breath, and appear pale in color. A decrease in the RBC count usually causes a decrease in the hemoglobin and hematocrit values.

Hemoglobin - Oxygen is carried to the tissues via hemoglobin in the RBC. Any drug which causes bone marrow suppression will decrease the hemoglobin level.

Hematocrit - The hematocrit is the percent of red blood cells in the fluid or blood plasma. This test is one of the truest markers of anemia. A decrease in hematocrit is always seen with a decrease in the hemoglobin. These two values are linked to one another.

Platelets - Platelets are cellular fragments which are produced by bone marrow and are necessary for the blood to clot. When activated by "trauma," platelets migrate to the site of injury where they become "sticky," adhering to the injured site and subsequently used in the developing fibrin clot (scab). Normal platelet values are 150,000-350,000. However, most people can survive without the threat of internal bleeding with counts above 50,000. Platelet count can drop dramatically following chemotherapy.

Normal Adult Values Male Female
RBC 4.5 - 6.0 M/ul 4.2 - 5.4 M/ul
Hemoglobin (HgB) 14 - 18 g/dL 12 - 16 g/dL
Hematocrit (Hct) 40 - 52% 37 - 47%

Note: Normal values will vary from laboratory to laboratory.

MCV - The mean cell volume or MCV is the most important of the RBC indices. It measures the average size of the RBC. RBC's that are larger or smaller than normal may indicate anemia. Vitamin B12 and Folic Acid deficiencies also cause increases in MCV.

MVP - MVP - Mean platelet volume measures the average size of platelets. Higher than normal MPV is associated with increased risk of heart attack and stroke.

The other 2 indices are not so important. They are the MCH (mean corpuscular hemoglobin) which measures the amount of hemoglobin in red cells and the MCHC (Mean corpuscular hemoglobin concentration) which measures the percent of hemoglobin in red cells. These are used to help diagnose various anemias and leukemias.

WBC Count - The WBC count is the number of WBC's in a cubic millimeter of blood. The primary function of these cells is to prevent and fight infections. There are many different types of white blood cells that play specific roles in fight infections. These specific types of WBC's can be measured in the white cell differential. WBC count can be decreased for a variety of reasons including certain medications, minor viral infections and stress.

Normal Adult Values
Lymphocytes 22-44%
Monocytes 0-7%
Neutrophils 40-70%
Eosinophils 0-4%
Basophils 0-1%

Note: Normal values will vary from laboratory to laboratory.

White Cell Differential - The white cell differential counts 100 white cells and differentiates them by type. This gives a percent of the different kinds of white cells in relation to one another. The three main types are: granulocytes, lymphocytes, and monocytes. Neutrophils are increased during bacterial infections while lymphocytes are decreased with viral infections. Increased monocytes are sometimes seen in chronic infections.

Basophils play a role in acute allergic reactions. They release histamine, heparin and other substances in response to the presence of allergens and cause increased vascular permeability, smooth muscle spasm, vasodilatation, and the clinical symptoms of an allergic reaction: watery eyes, runny nose, and difficult breathing.

Eosinophils are found in high numbers when the body is invaded by some parasites and during allergy attacks. They accumulate wherever allergic reactions like those in asthma take place.

CBC and Related Side Effects of Chemotherapy

The CBC helps determine side effects of chemotherapy, which usually include changes in the three types of cells in your blood, red, white and platelets. Because chemotherapy kills fast-growing blood cells as well as cancer cells, side effects involving your blood are an expected result of chemotherapy.

Typical side effects of chemotherapy involving blood include the following:

is the scientific name for a low infection-fighting white blood cell count. A low white blood cell count may leave your body vulnerable to infection or too weak to receive chemotherapy if you are currently in treatment. Neupogen or Neulasta may be prescribed to stimulate the production of new white blood cells

Anemia is the scientific name for a low red blood cell count. RBC's contain hemoglobin, a protein that carries oxygen from the lungs to the body's muscles and organs. Oxygen is critical to the health of your tissues and organs. If you are diagnosed with anemia while receiving chemotherapy to treat certain types of cancer, there are multiple treatment options. Two of these options are red blood cell transfusions and colony stimulating agents such as Procrit or Epogen which stimulate the production of red blood cells.

Thrombocytopenia is the scientific name for a low platelet count. A low platelet count may cause you to experience bruising or excessive bleeding. Platelets are often transfused when counts drop dramatically during chemotherapy.

Nadir Period
All rapidly dividing cells are affected by chemotherapy. These include hair, lining of the mouth & intestinal tract and blood cells including WBC's, RBC's and platelets. Stem cells grow more slowly so they are not affected. Therefore, the rapidly dividing mature cells are destroyed and it takes 3-4 weeks for the new stem cells to be working. The nadir is the time when cell counts are lowest and when a chemo patient is most susceptible to infection (low white cell count) and bleeding (low platelet count). The nadir time is usually about 10 days after treatment (but may vary with the chemo agents given) and blood counts return to normal within 3-4 weeks.

The next dose of chemo will not be given until counts return to normal or permanent damage to the bone marrow may result.

Sed Rate - Eosinophil Sedimentation Rate (ESR)

This test is a non-specific measure of inflammation.

The ESR is increased by any cause or focus of inflammation. When increased, It is useful for diagnosing diseases, such as multiple myeloma, temporal arteritis, polymyalgia, various auto-immune diseases, lupus, rheumatoid arthritis, and chronic kidney diseases. The ESR is decreased in sickle cell anemia, polycythemia, and congestive heart failure.

The basal ESR is slightly higher in females.

C-Reactive Protein (CRP)

A C-reactive protein (CRP) test is a blood test that measures the amount of a protein called C-reactive protein in your blood. C-reactive protein measures general levels of inflammation in your body.

High levels of CRP are caused by infections and many long-term diseases. But a CRP test cannot show where the inflammation is located or what is causing it. Other tests are needed to find the cause and location of the inflammation.

This test may be run to check for infection after surgery. CRP levels normally rise within 2 to 6 hours of surgery and then go down by the third day after surgery. If CRP levels stay elevated 3 days after surgery, an infection may be present. CRP is also used to Identify and track infections and diseases that cause inflammation, such as lymphoma, lupus, giant cell arteritis, rheumatoid arthritis inflammatory bowel disease and osteomyelitis.

Check to see how well treatment is working, such as treatment for cancer or for an infection. CRP levels go up quickly and then become normal quickly if you are responding to treatment measures.

A special type of CRP test, the high-sensitivity CRP test (hs-CRP), is sometimes done to determine a person's risk of heart disease. It can indicate the presence of inflammation which can be damaging to the inner lining of the arteries and increase the risk of heart attack. The connection between high CRP levels and heart attack risk is not very well-understood.

By Laurie Butt, RN
Nursing Supervisor