A 24-year-old primigravida at 20 weeks has haemoglobin 9.8 g/dL, MCV 62 fL, RBC count 5.8 million/mm3, and serum ferritin 30 ng/mL. Her husband is a known carrier of beta thalassaemia. Which test will best clarify the diagnosis?
- A Haemoglobin electrophoresis by HPLC ✓
- B Repeat peripheral smear examination
- C Serum iron studies
- D Osmotic fragility test
Correct answer: A. Haemoglobin electrophoresis by HPLC
Explanation
The Mentzer index (MCV divided by RBC count) here is about 10.7, below 13, pointing to beta thalassaemia trait rather than iron deficiency, and the normal ferritin argues against iron lack. Haemoglobin analysis by HPLC or electrophoresis showing raised HbA2 above 3.5 percent confirms the trait. This matters urgently because the husband is also a carrier, creating a 25 percent risk of thalassaemia major. Iron studies would be normal and add nothing, and osmotic fragility is obsolete for this purpose.
Reference: Williams Obstetrics, 26th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.