A 42-year-old woman presents with fatigue and dyspnea on exertion. On examination, she has pallor and glossitis. Her hemoglobin is 8.2 g/dL with MCV 62 fL. Which investigation is most specific for confirming iron deficiency anemia?
A. Reticulocyte count
B. Serum ferritin level
C. Serum iron and total iron-binding capacity (TIBC)
D. Bone marrow iron staining (Prussian blue stain)
Explanation
Confirmatory Investigation for Iron Deficiency Anemia
Why Bone Marrow Iron Staining is Gold Standard
Key Point
Prussian blue (Prussian blue) staining of bone marrow aspirate is the most specific and direct test for assessing iron stores. Absence of iron in macrophages is pathognomonic for iron deficiency.
High-YieldNEET PG
While serum ferritin and TIBC are useful screening tests, they can be falsely elevated in inflammation, infection, and malignancy. Bone marrow examination directly visualizes iron stores and rules out other causes of microcytic anemia (thalassemia, sideroblastic anemia).
Investigation Hierarchy for Iron Deficiency
Table
Investigation
Sensitivity
Specificity
Limitation
Serum ferritin
High
Low (↑ in inflammation)
Acute phase reactant
Serum iron + TIBC
Moderate
Moderate
Diurnal variation, affected by diet
Transferrin saturation
Good
Good
Still affected by inflammation
Bone marrow iron stain
Very high
Very high (gold standard)
Invasive, not routine
Clinical Pearl
In clinical practice, iron studies (ferritin + TIBC + serum iron) are first-line because they are non-invasive. Bone marrow examination is reserved for:
