A 24-year-old primigravida at 18 weeks has haemoglobin 9.8 g/dL, MCV 62 fL, RBC count 5.8 million/mm3, and serum ferritin 45 ng/mL. Her Mentzer index is 10.7. Which investigation will confirm the underlying diagnosis?

• A Bone marrow examination
• B Peripheral smear for schistocytes
• C Serum transferrin receptor assay
• D Haemoglobin electrophoresis showing raised HbA2 above 3.5 percent ✓

Explanation

Mentzer index below 13 (MCV divided by RBC count) with a normal ferritin points to beta thalassaemia trait rather than iron deficiency, which typically gives a ratio above 13. Confirmation is by haemoglobin electrophoresis demonstrating elevated HbA2 greater than 3.5 percent. Bone marrow is unnecessary, and schistocytes suggest microangiopathy. Partner testing follows diagnosis because a fetus at risk of thalassaemia major needs counselling and prenatal diagnosis.

Reference: Harrison's Principles of Internal Medicine, 21st ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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