RDW
What it measures, and what changes the number.
RDW, or red cell distribution width, describes how much red blood cells vary in size within a sample. The analyzer measures the size of thousands of cells and reports how wide that spread is. A term for size variation is anisocytosis.
It is read alongside MCV, the average red cell size, and the other red cell indices such as MCH, together with hemoglobin and the red cell count. Iron studies such as ferritin, and vitamin B12 or folate, are often looked at next to it because these affect red cell size.
RDW can be reported in two ways, as a coefficient of variation (RDW-CV) or as a standard deviation in femtoliters (RDW-SD), and the two are not interchangeable. Analyzer brands also differ. Reports may use Amplitud distribució eritrocitària (ADE) or Indice de anisocitosis (RDW).
Often read alongside: MCV, MCH, Hemoglobin, Red blood cells, Ferritin