A 24-year-old woman has mild anemia discovered on routine testing: Hb 10.5 g/dL, MCV 64 fL, normal serum ferritin. The Mentzer index (MCV/RBC count) is calculated at 10. Hemoglobin electrophoresis shows HbA2 of 5.8%. What is the most likely diagnosis?

• A Iron deficiency anemia
• B Alpha-thalassemia trait
• C Anemia of chronic disease
• D Beta-thalassemia minor ✓

Explanation

In beta-thalassemia minor, impaired beta chain production causes compensatory elevation of delta chains, so HbA2 above 3.5% is diagnostic. A Mentzer index below 13 also favors thalassemia over iron deficiency, where the index typically exceeds 13. Iron deficiency would show low ferritin and normal or low HbA2, and anemia of chronic disease gives a low-normal HbA2 with high ferritin. Alpha-thalassemia trait leaves HbA2 normal because delta chains are unaffected.

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

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Written and medically reviewed by the StethoPrep medical team.