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Conrad ME.


In: Walker HK, Hall WD, Hurst JW, editors.


Clinical Methods: The History, Physical, and Laboratory Examinations. 3rd edition. Boston: Butterworths; 1990. Chapter 147.


Anemia is defined as a decrease in the red blood cell mass. Accurate measurements require labeling of erythrocytes followed by in vivo quantification of the dilution of the labeled cells in the circulation. Obviously, this is an impractical method for the detection of anemia, and measurements of either the hemoglobin concentration, the hematocrit, or red blood cell count are used. Each of these latter methods is complicated by the fact that they represent concentrations that can be altered by variations in the plasma volume without changes in the red blood cell mass. Usually this is usually not important in the clinical setting for the detection of anemia, but it should be considered by the physician. The World Health Organization has decided that anemia exists in adults whose hemoglobin values are lower than 13 g/dl in males and 12 g/dl in females. Children age 6 months to 6 years are considered anemic at hemoglobin levels below 11 g/dl; and between 6 and 14 years, below 12 g/dl. The disadvantage of these arbitrary criteria is that they include some normal individuals who fall below the defined value. In the United States, slightly higher values are usually cited, and males with a hemoglobin below 13.5 g/dl and females with a hemoglobin below 12.5 g/dl probably should be considered anemic. Higher values are anticipated in individuals living at altitudes significantly above sea level. In conditions in which there is an increase in the plasma volume, such as the last trimester of pregnancy, lower hemoglobin values will be encountered even though the red cell mass is normal.

Copyright © 1990, Butterworth Publishers, a division of Reed Publishing.

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