How do ferritin and transferrin saturation help differentiate iron deficiency anemia from anemia of chronic disease?

• A. Iron deficiency: low ferritin and low transferrin saturation; anemia of chronic disease: normal or high ferritin with low transferrin saturation.
• B. Iron deficiency: high ferritin and high transferrin saturation; anemia of chronic disease: normal ferritin with high transferrin saturation.
• C. Iron deficiency: ferritin high; transferrin saturation low; anemia of chronic disease: ferritin low; transferrin saturation low.
• D. Iron deficiency: ferritin low; transferrin saturation high; anemia of chronic disease: ferritin high; transferrin saturation high.

Answer: (A)

Ferritin reflects stored iron, while transferrin saturation shows how much iron is actually bound to transferrin in circulation. In iron deficiency, stores are depleted, so ferritin falls and serum iron is also low, making transferrin saturation low as well. In anemia of chronic disease, inflammation makes ferritin rise or stay normal (ferritin is an acute‑phase reactant) while iron is withheld from circulation, so serum iron remains low and transferrin saturation is low, but ferritin is normal or high. Therefore, the pattern is low ferritin and low transferrin saturation for iron deficiency, versus normal/high ferritin with low transferrin saturation for anemia of chronic disease.