RED CELL DISTRIBUTION WIDTH; RDW

RDW measures the variability in red blood cell size & is very useful in evaluating anisocytosis. A low MCV & high RDW are most likely due to iron deficiency anemia. RDW is often normal in milder forms of thalassemia. A combination of high or normal RBC count, low MCV & normal RDW is a common pattern in thalassemia trait.