Blood Count in Humans
A complete blood count, or CBC, is a common blood test that is performed as part of a routine physical or to assist in diagnosing disease. A small blood sample is needed and must be collected in a lavender top tube that has the additive EDTA. This additive helps prevent clotting. This test looks at the components of the blood, red cells, white cells and platelets and provides specific information about the size and shape and number of those cells. A CBC also delivers information about the levels of hemoglobin and hematocrit in a person's blood, which, if low, are indicators or anemia.
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Red Blood Cells
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The red blood cell count is also found in a CBC. This count is extremely important and numbers that are high or low are indicative of different conditions. Red cells transport oxygen to the tissues of the body and carry away carbon dioxide. Therefore, if the count is low, the patient may be suffering from anemia and not be receiving enough oxygen to the tissues. If the count is high, it can be indicative of polycythemia where it is possible that the cells clump together and cause small clots.
White Blood Cells
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Every CBC contains a white blood cell count. This count assists in diagnosing disease and infection. White cells, or leukocytes, increase in numbers if bacterial infection, inflammation or allergic reaction is occurring in the body. If the overall number of white blood cells is high, a physician will know to look for an underlying cause. The white cell count is also useful for monitoring patients undergoing cancer treatment, which often destroys white cells.
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Platelet Count
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A CBC also contains information about the number of platelets found in the blood. Since platelets are primarily involved in the blood clotting process, the amount in the blood is extremely important. A level that is too high might mean the patient is at risk for blood clots while a level that is too low may mean the patient is at risk for significant bleeding. Some inherited disorders, such as lupus, also see abnormalities of the platelet count.
Hemoglobin, Hematocrit and Red Cell Indices
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Hemoglobin and hematocrit usually mimic the red cell count. These are often indicators of anemia if levels are low or if levels are high, that can be indicative of dehydration. The red cell indices look at the individual red cells for any structural changes. It measures the size of the cells and the concentration of hemoglobin and hematocrit in an individual red cell. These results are usually used in determining the type, if any, of anemia present.
Differential
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The differential of the CBC consists of examination of the white blood cells. There are five different types of white blood cells and the differential determines what percentage of each is found in the sample. This can be clinically important since different types of white cells are increased based on different conditions. Allergic reactions increase the level of eosinophils, while bacterial infections increase the amount of neutrophils and monocytes. While the CBC is generally an automated test performed by a machine, a highly trained technologist frequently performs a manual differential to be assured of the accuracy of the results.
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