What Is a CBC Blood Test?
A complete blood count (CBC) is a routine blood test that is performed by collecting a small blood sample in a lavender top tube, which has EDTA, an additive, to prevent the blood from clotting. This test examines the size, shape and number of cells in the blood and also provides information about the hemoglobin and hematocrit levels in the blood.
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White Cells
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The white blood cell, or leukocyte, count assists in diagnosing infection and disease. Leukocytes increase if there is an allergic reaction, bacterial infection or inflammation occurring in the body.
Red Cells
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Red blood cells, or erythrocytes, transport oxygen to the body tissues and carry away waste. This count is extremely important and both high and low levels are indicative of various conditions.
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Platelets
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The amount of platelets in a blood sample is important, since platelets are involved in the blood clotting process. A high level may mean the patient is predisposed to blood clots, while a low level may put him at risk of a bleed.
Hemoglobin and Hematocrit
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Hemoglobin and hematocrit are usually in line with the red cell count. If levels are low, anemia is considered. High levels may mean dehydration.
Red Cell Indices
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Red cell indices look for structural changes and the levels of hemoglobin and hematocrit in the individual erythrocytes. This is useful in determining what type of anemia, if any, is present.
Differential
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The differential is the examination of the leukocytes. It is clinically important since it determines the percentage of each of the five different types of white cells.
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