What Is A CBC Blood Test?


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Anonymous Profile
Anonymous answered

Complete Blood Count (CBC)

A complete blood count (CBC) gives important information about the kinds and numbers of cells in the blood, especially red blood cells, white blood cells, and platelets. A CBC helps your health professional check any symptoms, such as weakness, fatigue, or bruising, you may have. A CBC also helps him or her diagnose conditions, such as anemia, infection, and many other disorders.
A CBC test usually includes:

  • White blood cell (WBC, leukocyte) count. White blood cells protect the body against infection. If an infection develops, white blood cells attack and destroy the bacteria, virus, or other organism causing it. White blood cells are bigger than red blood cells but fewer in number. When a person has a bacterial infection, the number of white cells rises very quickly. The number of white blood cells is sometimes used to find an infection or to see how the body is dealing with cancer treatment.

  • White blood cell types (WBC differential). The major types of white blood cells are neutrophils, lymphocytes, monocytes, eosinophils, and basophils. Immature neutrophils, called band neutrophils, are also part of this test. Each type of cell plays a different role in protecting the body. The numbers of each one of these types of white blood cells give important information about the immune system. Too many or too few of the different types of white blood cells can help find an infection, an allergic or toxic reaction to medicines or chemicals, and many conditions, such as leukemia.

  • Red blood cell (RBC) count. Red blood cells carry oxygen from the lungs to the rest of the body. They also carry carbon dioxide back to the lungs so it can be exhaled. If the RBC count is low (anemia), the body may not be getting the oxygen it needs. If the count is too high (a condition called polycythemia), there is a chance that the red blood cells will clump together and block tiny blood vessels (capillaries). This also makes it hard for your red blood cells to carry oxygen.

  • Hematocrit (HCT, packed cell volume, PCV). This test measures the amount of space (volume) red blood cells take up in the blood. The value is given as a percentage of red blood cells in a volume of blood. For example, a hematocrit of 38 means that 38% of the blood's volume is made of red blood cells. Hematocrit and hemoglobin values are the two major tests that show if anemia or polycythemia is present.

  • Hemoglobin (Hgb). The hemoglobin molecule fills up the red blood cells. It carries oxygen and gives the blood cell its red color. The hemoglobin test measures the amount of hemoglobin in blood and is a good measure of the blood's ability to carry oxygen throughout the body.

  • Red blood cell indices. There are three red blood cell indices: Mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH), and mean corpuscular hemoglobin concentration (MCHC). They are measured by a machine and their values come from other measurements in a CBC. The MCV shows the size of the red blood cells. The MCH value is the amount of hemoglobin in an average red blood cell. The MCHC measures the concentration of hemoglobin in an average red blood cell. These numbers help in the diagnosis of different types of anemia. Red cell distribution width (RDW) can also be measured which shows if the cells are all the same or different sizes or shapes.

  • Platelet (thrombocyte) count. Platelets (thrombocytes) are the smallest type of blood cell. They are important in blood clotting. When bleeding occurs, the platelets swell, clump together, and form a sticky plug that helps stop the bleeding. If there are too few platelets, uncontrolled bleeding may be a problem. If there are too many platelets, there is a chance of a blood clot forming in a blood vessel. Also, platelets may be involved in hardening of the arteries (atherosclerosis).

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Anonymous commented
Lol...Cut and paste will get the correct info to people, especially in regards to health issues or questions. WebMd is a good site for these people to check.....
Mati green Profile
Mati green answered
Hmmm..nice cut and paste...lol... A CBC is complete blood count. It is a manuel count of all red blood cells, white blood cells, and platelets. The red blood and platelet counts are preformed with a small amount of diluted whole blood on a specialized glass slide called a hemocytometer. The hemocytometer is placed under the microscope, and the red cells and platelets are manually counted by using the tiny etched grid on the slide. The white blood count is done on a normal glass slide with a prepared peripheral blood smear. This uses only one drop of blood. The white cells are viewed under low power and counted. We usually count 10 fields and with a formula make the estimate of how many wbc's we see in those 10 fields. We then  go to high power and count 100 actual cells keeping track of how many of each of the 5 different white blood cells we see. CBC's are My favorite part of my hematology class. I'm not going to go into anymore detail since Dc4580 pretty much covered it..I just wanted to add a little about the actual test procedure.
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Anonymous commented
Hi Mati--I was wondering if you might be able to suggest a source where I can read up on how to manually read CBCs...your description above is so helpful! Is there any such thing as a step by step manual on how to read these? Thank you!
Charming Gurl Profile
Charming Gurl answered
The complete blood count (CBC) is one of the most commonly ordered blood tests. The complete blood count is the calculation of the cellular (formed elements) of blood. These calculations are generally determined by special machines that analyze the different components of blood in less than a minute.
A major portion of the complete blood count is the measure of the concentration of white blood cells, red blood cells, and platelets in the blood.

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