A 24-year-old woman is evaluated for mild microcytic anemia: Hb 10.8 g/dL, MCV 63 fL, total RBC count 6.0 million/mm3. Serum ferritin is 55 ng/mL, serum iron and transferrin saturation are normal. Using the Mentzer index, the most likely diagnosis is:
- A Iron deficiency anemia
- B Anemia of chronic disease
- C Beta-thalassemia trait ✓
- D Sideroblastic anemia
Correct answer: C. Beta-thalassemia trait
Explanation
Mentzer index equals MCV divided by RBC count in millions. Here it is 63 divided by 6.0, which is about 10.5. A value below 13 favors thalassemia trait because RBC counts are preserved or raised, while a value above 13 favors iron deficiency. Normal ferritin and iron studies exclude iron deficiency and anemia of chronic disease. In Indian exam convention, Mentzer index remains a standard bedside discriminator before HPLC.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
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