Red blood cell distribution width

Image:Redbloodcells.jpg The red blood cell distribution width, or RDW, is a measure of the variation of red blood cellvolume that is reported as part of a standard complete blood count. Usually red blood cells are a standard size. Certain disorders, however, cause a significant variation in cell size. Higher numbers indicate greater variation in size. Normal range is 11 - 15%. If anemia is observed, RDW test results are often used together with MCVresults to figure out what the cause of the anemia might be. It is mainly used to differentiate between iron deficiency anemiaand other microcytic anemiasin children.

Mathematically the RDW is calculated with the following formula:

RDW = (Standard deviation of red cell volume ÷ mean cell volume) × 100

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It uses material from the http://en.wikipedia.org/wiki/Red+blood+cell+distribution+width Wikipedia article Red blood cell distribution width.