A 24-year-old primigravida at 18 weeks has haemoglobin 9.8 g/dL, MCV 64 fL, RDW 14%, serum ferritin 35 ng/mL, and her husband's haemoglobin is normal. Her Mentzer index (MCV/RBC count) is 19. What is the most likely diagnosis?
- A Iron deficiency anaemia
- B Beta thalassaemia trait ✓
- C Anaemia of chronic disease
- D Sideroblastic anaemia
Correct answer: B. Beta thalassaemia trait
Explanation
A Mentzer index below 13 suggests beta thalassaemia trait, while a value above 13 favours iron deficiency anaemia. Here the index of 19 points to iron deficiency, but the ferritin of 35 ng/mL is adequate, excluding iron deficiency. The low MCV with normal ferritin and normal RDW fits thalassaemia trait, which shows microcytosis out of proportion to anaemia. Anaemia of chronic disease typically gives a normal or high ferritin with low transferrin saturation, and sideroblastic anaemia is rare in this setting.
Reference: Williams Obstetrics, 26th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.