Red Cell Distribution Width (RDW)

The red blood cell distribution width (RDW) is a measure of variation red blood cell (RBC) size. It is easily calculated by dividing the SD of erythrocyte volumes for the mean corpuscular volume. A modern refinement is the Red Cell Distribution width (RDW), which is a measurement of the variation in size of the RBC, and attempts to give a figure to the degree of anisocytosis, this being a morphological term indicating how much the cells vary in size.