Question

A Mentzer index of more than 13 suggests a diagnosis of which condition?

• A. Iron deficiency anemia
• B. Thalassemia
• C. Hereditary spherocytosis
• D. Autoimmune hemolytic anemia

Hint:

MCV divided by RBC count above 13 points away from thalassaemia.

Answer 1

The Correct Option is A

Step 1: The Mentzer index helps differentiate iron deficiency anaemia from beta thalassaemia. It is calculated as the mean corpuscular volume (MCV in fL) divided by the red blood cell count (RBC in millions per microlitre).

Step 2: The rule: if the index is greater than 13, iron deficiency anaemia is more likely; if it is less than 13, thalassaemia is more likely. Since the value here is more than 13, the answer is option a, iron deficiency anaemia.

Step 3: Reason: in iron deficiency the marrow makes fewer and smaller red cells, so both the RBC count and MCV fall, and dividing a low MCV by a low RBC count gives a value above 13.

Step 4: In thalassaemia the globin synthesis defect produces a normal or high RBC count with a low MCV, so dividing a low MCV by a normal/high RBC count gives a value below 13. Hereditary spherocytosis and autoimmune haemolytic anaemia are not differentiated by this index.