Red blood cell distribution width—a marker of fundamental importance?

The full or complete blood count is one of the most frequently requested diagnostic pathology tests which is used to diagnose and treat of many diseases. A common component of these tests is the red cell distribution width or red blood cell distribution width (RDW) which is the variation in the red blood cell (RBC) volumes (usually expressed as the coefficient of variation) and analogous to the qualitative anisocytosis. Red cells can vary in size between 60 fL (microcytosis) and 150 fL (macrocytosis).