A 26-year-old woman of Indian origin has mild microcytic hypochromic anemia unresponsive to oral iron. MCV 74 fL, RDW normal, Mentzer index below 13. Hemoglobin electrophoresis shows HbA2 2.0% and HbF 0.5%, essentially normal. Which investigation will establish the diagnosis?
- A Repeat hemoglobin electrophoresis after iron therapy
- B Bone marrow iron stain for ring sideroblasts
- C Alpha globin gene deletion analysis by PCR ✓
- D Osmotic fragility test
Correct answer: C. Alpha globin gene deletion analysis by PCR
Explanation
Alpha-thalassemia trait (two gene deletions) produces microcytosis with normal hemoglobin electrophoresis because there is no excess of unmatched alpha chains to raise HbA2 or HbF, unlike beta-thalassemia minor where HbA2 exceeds 3.5%. Diagnosis therefore requires molecular testing for alpha gene deletions. Electrophoresis will remain normal regardless of iron status, ring sideroblasts indicate sideroblastic anemia, and osmotic fragility is reduced in thalassemia but does not distinguish alpha from beta trait.
Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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