Iron Deficiency Anemia MCQ — NEET PG Practice Question | NEETPGAI
Iron Deficiency Anemia
hard
microscope Pathology
A 28-year-old woman with heavy menstrual bleeding presents with fatigue. CBC shows Hb 9.2 g/dL, MCV 68 fL, and RBC count 5.2 × 10^6/μL. Serum ferritin is 8 ng/mL. Which investigation would be most useful to differentiate iron deficiency anemia from thalassemia trait in this patient?
A. Serum transferrin saturation
B. Reticulocyte count
C. Mentzer index (MCV/RBC count)
D. Peripheral blood smear with target cells
Explanation
Differentiating Iron Deficiency from Thalassemia Trait
The Mentzer Index: A Simple Discriminator
Key Point
The Mentzer index (MCV/RBC count) is a simple, cost-effective calculation that distinguishes iron deficiency anemia from thalassemia trait:
Mentzer index <13 = Thalassemia trait (low MCV with relatively preserved RBC count)
Mentzer index >13 = Iron deficiency anemia (low MCV with low RBC count)
High-YieldNEET PG
In this case:
Mentzer index = 68 / 5.2 = 13.1 → Suggests iron deficiency anemia
The high RBC count (5.2 × 10^6/μL) despite low MCV is typical of thalassemia; iron deficiency usually shows both low MCV AND low RBC count
Why Mentzer Index Works
Table
Feature
Iron Deficiency
Thalassemia Trait
MCV
↓ (often <70)
↓ (often 60–70)
RBC count
↓
Normal or ↑
Mentzer index (MCV/RBC)
>13
<13
Serum ferritin
↓
Normal
TIBC
↑
Normal
Clinical Pearl
The Mentzer index is useful as a screening tool but is not diagnostic. In this patient, the low ferritin (8 ng/mL) already strongly suggests iron deficiency. The Mentzer index provides additional support and helps exclude thalassemia trait, which would present with normal ferritin.
Mnemonic: MENT-13 — Mentzer index <13 = thalassemia, >13 = iron deficiency
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