Red cell distribution width as a differential parameter between iron deficiency anemia and a-thalassemia: an empirical approach

Iron deficiency anemia (IDA) and thalassemia minor are the most common hypochromic microcytic anemias in the world. Different formulas have been proposed to differentiate IDA from beta thalassemia minor. However, yet no formula has been proposed to differentiate IDA from alpha thalassemia minor, and Hb electrophoresis is not helpful in this hemoglobinopathy. Red cell distribution width (RDW) as indicator of changes in red blood cell size is primarily employed to differentiate IDA from other microcytic anemias. An empirical approach involving iron therapy over 1 month has shown that an increase in Hb concentration by 1 g/dL over this period is indicative of IDA, while no changes in Hb concentration are suggestive of alpha thalassemia. RDW measured after iron therapy in order to differentiate IDA and related disorders from alpha thalassemia is a better index than an increased reticulocyte count. Due to the high prevalence of IDA and costly and time-consuming nature of specific diagnostic tests, the RDW index is considered as a very sensitive and cost-effective tool in the differential diagnosis of IDA.