In differentiating iron deficiency anemia from thalassemia, what parameter is increased in iron deficiency?

In iron deficiency anemia, the red blood cell distribution width (RDW) is increased. RDW reflects the variability in the size of red blood cells; as the body struggles to produce adequate red blood cells due to a lack of iron, it typically results in a greater range of cell sizes. In iron deficiency anemia, you will often see a mixture of smaller microcytic cells and normal-sized cells, which contributes to an increased RDW.

In contrast, thalassemia is characterized by a more uniform population of red blood cells, which leads to a normal or even decreased RDW. Other parameters, such as mean corpuscular volume (MCV) and ferritin, exhibit different behaviors in these conditions. In iron deficiency anemia, the MCV is usually decreased due to the smaller size of the red blood cells, while ferritin levels are also low, reflecting reduced iron stores. The RBC count can be variable but is often decreased in both conditions. Thus, the increase in RDW is a key distinguishing feature that helps differentiate iron deficiency anemia from thalassemia.