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a. The hematocrit or the packed-cell volume is the percentage of the total volume of red blood cells in relation to the total volume of whole blood. The term "hematocrit" is derived from two Greek words: Hemato, meaning blood; and Krites, meaning to judge (then reduced to crit, meaning to separate). The procedure is performed by filling a capillary tube with blood and centrifuging at a constant speed for a constant period of time. The packet cell volume is then measured. The hematocrit can also be determined by automated sequential analyzers but is usually a calculated value.

b. The hematocrit is the most useful single index for determining the degree of anemia or polycythemia. It can be the most accurate (2-4 percent error) of all hematological determinations. In contrast, the direct red blood cell chamber count has a percent error of 8-10 percent. The hematocrit is, therefore, preferable to the red blood cell count as a screening test for anemia. The values for the hematocrit closely parallel the values for the hemoglobin and red blood cell count.

Curriculum design: David L. Heiserman
Publisher: SweetHaven Publishing Services

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