Red blood cell distribution width

The red cell distribution width ( EVB ), which is also known in German-speaking countries often with the English abbreviation RDW ( Red Blood Cell Distribution Width), is a parameter which is determined in laboratory medicine as part of a blood count. Determining the EVB, which is expressed in percent and is a measure of the size distribution of red blood cells ( erythrocytes) is carried in the blood by flow cytometry. It is calculated from the standard deviation of the volume ( Sv) of the erythrocytes and the mean erythrocyte volume ( MCV) by the formula

The size distribution of red blood cells in healthy patient corresponds to a line extending approximately from six to nine micrometers in diameter normal distribution bell curve, which is known as a Price-Jones curve after the English pathologist Cecil Price -Jones. Your maximum is 120 by 500 cells at about 7.5 microns. The normal thickness of the formed as a concave circular disks erythrocytes is approximately two micrometers on the edge and about one micrometer in the middle. The EVB is mainly dependent on the diameter of the erythrocytes and thus correlates to some extent with the width of the Price-Jones curve. But in addition, the thickness of the red blood cells have an effect on the EVB. They thus describes the inequality ( anisocytosis ) in erythrocyte in shape and size.

The reference range for the EVB is 11.5 to 14.5 percent. Greatly increased values ​​are an indication of the existence of different forms of anemia, such as hemolytic anemia, iron deficiency anemia, pernicious anemia or a ball of a cell anemia. In addition, may indicate a significant excess over the reference area on a myelofibrosis. An elevated finding is, however, generally not considered in isolation, but is used in conjunction with other laboratory values ​​for differential diagnosis. Values ​​below the reference range, however, of no clinical relevance. In general, the EVB is attached no great importance in clinical practice.