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NetWellness provides the highest quality health information and education services created and evaluated by faculty of our partner universities.
Saturday, March 20, 2010
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NetWellness provides the highest quality health information and education services created and evaluated by faculty of our partner universities.
Saturday, March 20, 2010
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A complete blood count (CBC) is taken to identify and measure the different kinds of cells that make up the blood. This test measures what are commonly called the red cells and the white cells. Most diseases of the blood and lymphatic systems such as leukemia are uncovered by a standard blood test. Blood is drawn from a vein in the arms and sent to a laboratory for the CBC. Red blood cells usually occur as one type known as a mature reticulocyte. White blood cells occur as a number of different types including neutrophils, basophils, and lymphocytes. An increase in white blood cells means there is an infection in the body. White blood cells can be measured by automated machines which are able to tell one type of white cell from another. Such machines can identify another group of cells called platelets, which are responsible for blood clotting.
Red blood cells, white blood cells, and platelets are components of blood that can be analyzed with automated machines. Depending upon how sophisticated they are, the machines can break down the types of white cells into several classes. In addition, they can measure the size and concentration of hemoglobin inside a red cell. These measurements are important for determining a number of different types of diseases. For example, deficiencies of the vitamins folate and b12 affect the size of red blood cells. Such measurements can be determined by running an initial screen, which would come out of a CBC done with the usual automated instruments.
Machines are limited in what they can do. As a result, a peripheral blood smear is made to learn information that cannot be picked up by a CBC. A drop of blood is taken from the tube collected for the CBC and then put onto a slide, spread out, and stained. This is done so that the white cells, red cells, and platelets can be examined under a microscope by a trained technologist or pathologist. The peripheral blood smear has enormous importance because there are some diseases which cannot be identified by the CBC. A trained individual performing a peripheral blood smear can count the number of blood cells, the type of each cell, as well as determine the special characteristics of each cell. This can help diagnose certain kinds of white cell cancers. In addition the absence of platelets and the damage to red blood cells can also be determined by a peripheral blood smear. Since the peripheral blood smear is examined by a trained individual, the process is fairly slow compared to an automated machine. As a result, most laboratories do as few peripheral blood smears as possible. The exception is in cases when the laboratory has a large number of patients with various types of blood problems such as cancers, and in cases of patients who are bleeding because they are losing their platelets.
This article is a NetWellness exclusive. 
Last Reviewed: Aug 09, 2000
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Amadeo Pesce, PhD Professor Emeritus Department of Pathology and Laboratory Medicine College of Medicine University of Cincinnati |
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