A 28-year-old woman with heavy menstrual bleeding has hemoglobin 8.9 g/dL and MCV 68 fL. Which combination of laboratory findings best supports a diagnosis of iron deficiency anemia rather than anemia of chronic disease?

• A Low serum ferritin, raised total iron binding capacity, low transferrin saturation ✓
• B Low serum iron, low total iron binding capacity, normal ferritin
• C High serum ferritin, low total iron binding capacity, normal transferrin saturation
• D Normal serum ferritin, raised serum iron, raised transferrin saturation

Explanation

In iron deficiency, storage iron is depleted first, so ferritin falls, while the liver upregulates transferrin, raising total iron binding capacity and lowering transferrin saturation below about 16 percent. In anemia of chronic disease, interleukin-6 driven hepcidin traps iron in macrophages, giving low serum iron but also LOW total iron binding capacity with a normal or high ferritin, because ferritin is an acute phase reactant. Option B is therefore the classic chronic disease pattern and the most tempting distractor.

Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.

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