Which laboratory determinations would be most helpful in distinguishing iron deficiency anemia from anemia of chronic disease?

This is a common clinical scenario in real life. Serum ferritin is markedly decreased in iron deficiency anemia and is normal to modestly elevated in anemia of chronic disease. This difference makes this test very useful in this setting. You should be aware that serum ferritin may behave like an acute phase reactant. Therefore, in an acute inflammatory situation, erythrocyte ferritin may be more reliable if serum ferritin is equivocal. Also, do not forget that iron deficiency anemia can complicate the anemia of chronic disease (e.g., gastrointestinal bleeding can complicate gastrointestinal cancers); in this situation, most physicians treat the apparent iron deficiency anemia and see to what degree the anemia corrects. The erythrocyte: granulocyte ratio in bone marrow is slightly decreased in both iron deficiency anemia and anemia of chronic disease, but may be markedly increased in sideroblastic anemias. Polychromatophilic target cells and stippled erythrocytes are absent in both iron deficiency anemia and anemia of chronic disease, but may be present in sideroblastic anemias and other iron-utilization anemias. Ref - Harrison's principles of internal medicine 20e pg 685,686,688