A 26-year-old woman has mild anemia (hemoglobin 10.8 g/dL) with MCV 66 fL and a strikingly high RBC count of 6.4 million/mm3. Iron studies are normal and ferritin is adequate. Which single laboratory result would best confirm beta-thalassemia trait over iron deficiency?

• A Serum soluble transferrin receptor level above normal
• B Peripheral smear showing schistocytes
• C Hemoglobin A2 greater than 3.5 percent on electrophoresis ✓
• D Bone marrow showing more than 15 percent ring sideroblasts

Explanation

In beta-thalassemia trait, reduced beta chain production leads to relative excess of delta chains, so HbA2 rises above 3.5 percent, the standard confirmatory cutoff used in Indian exam practice. The high RBC count with disproportionately low MCV (low Mentzer index, MCV/RBC below 13) already points toward thalassemia trait rather than iron deficiency. Soluble transferrin receptor rises in iron deficiency, schistocytes indicate fragmentation hemolysis, and ring sideroblasts define sideroblastic anemia, none of which apply here.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.