What laboratory test is best for differentiating iron deficiency anemia from other types of anemias?

Ferritin is the most reliable laboratory test for distinguishing iron deficiency anemia from other forms of anemia. Ferritin is a protein that stores iron and releases it in a controlled fashion; therefore, it reflects the body's iron stores. In cases of iron deficiency anemia, the ferritin levels are typically low, indicating depleted iron stores.

In contrast, other types of anemia, such as anemia of chronic disease or hemolytic anemia, may present with normal or even elevated ferritin levels because the iron stores may still be present even when there is anemia. This unique characteristic of ferritin makes it a crucial test in diagnosing iron deficiency anemia and differentiating it from other anemias that may have similar symptoms but different underlying causes.

Hematocrit and hemoglobin are also important measures when assessing anemia, but they do not provide specific information about iron stores. The reticulocyte count assesses the bone marrow's response to anemia but does not specifically indicate the type of anemia concerning iron deficiency.