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$Title{Complete Blood Count}
A Medical Times Patient Education Chart
(C) Romaine Pierson Publishers, Inc.
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What Can the Blood Tests Tell?
The tests done as part of a complete blood count (CBC) are useful in
diagnosing some illnesses. The major ones are anemia (which is a shortage of
red blood cells or of hemoglobin, the blood protein that carries oxygen) and
leukemia (which is a type of cancer that causes abnormal increases in white
blood cells). CBCs can also help track progress in treating diseases.
The blood sample is usually taken from a vein in the arm, but may be
drawn from the foot, finger, or ear. Your doctor will use the blood test
results along with the results of your physical exam to diagnose a disease or
assess your health.
Test results will vary even in healthy people because of personal
differences such as age and sex. The normal ranges given here are for adults.
Although the measurement terms may be unfamiliar, they are used here so you
can compare them with your own test results.
The Red Blood Cell Count
The number of red blood cells (RBCs) within the normal range varies from
3.6 to 5.4 million per cubic millimeter. The average for females is 4.5
million and for males 5 million. Too many RBCs might be a sign of lung
disease or congestive heart failure, the inability of the heart to pump blood
efficiently. Too few RBCs, a condition known as anemia, can be caused by
bleeding, leukemia, kidney disease, hormone problems, and other chronic
diseases. Radiation and drugs used to treat cancer and other conditions may
damage the bone marrow, where RBCs are formed, and so prevent the formation of
enough new RBCS.
Hemoglobin: The Oxygen Carrier
Hemoglobin is the red pigment in RBCs that binds with oxygen, so the
amount of hemoglobin is a measure of how much oxygen the RBCs are capable of
carrying to other cells. The normal levels range from 12 to 16 grams per
deciliter for women and 13.5 to 18 for men. Low levels can result from
inherited anemias, such as sickle cell anemia and thalassemia, or from anemias
due to iron and vitamin deficiencies.
The Hematocrit: Ratio of Red Blood Cells
The hematocrit measures the percentage of blood volume made up of RBCs.
The nominal ranges are 37% to 47% for women and 40% to 54% for men. Anemia,
leukemia, blood loss, and kidney failure cause lower levels. Lung disease and
loss of body fluids, such as that which occurs with severe burns, surgery, and
shock, could result in higher percentages of RBCs.
White Blood Cells: The Defense Team
In normal adults, the total number of white blood cells ranges from 4,000
to 10,000 per cubic millimeter. Higher levels could be caused by infection,
leukemia, acute bleeding, stress, and conditions that cause damage to the
cells, such as heart attacks. Radiation, viral illness, and a weakened immune
system are some of the causes of a decreased number of WBCs.
Each of the five different types of white blood cells performs a special
job in defending the body against bacteria and other harmful matter. The
percentage of each type of WBC in the blood is measured by the differential
count or "diff." (See front of chart for WBC types and normal ranges.)
Neutrophils and monocytes are the cells most active against bacterial
infections. Lymphocytes help produce antibodies that can inactivate harmful
substances entering the body, including infectious agents. Eosinophils and
basophils are involved in allergies.
The Red Blood Cell Indices
Three measurements, known as the red cell indices, can help your doctor
identify the specific types of anemia. Knowing the type of anemia and its
possible cause makes it possible to treat the disease appropriately.