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A 30 yrs old female, RBC count 4.5 million, MCV 55fl, TLC 8000, no history of blood transfusion. What is the likely diagnosis?
Low MCV (nl 80 - 100) rules out 4. Absence of transfusion rules out 2. So we have to distinguish between 1 &2.
In IDA, the RBC count is usually less due to decreased production. Whereas in thalassemias, RBC are produced but hemoglobin is defective.
Use Mentzer index.
The Mentzer index is used to differentiate iron deficiency anemia from beta thalassemia.
It is calculated from the results of a complete blood count. If the quotient of the mean corpuscular volume divided by the red blood cell count is less than 13, thalassemia is more likely. If the result is greater than 13, then iron-deficiency anemia is more likely.
Here it is 55/4.5 < 13
This test helps in differentiating iron deficiency from Thalassemia. In Iron deficiency, the marrow can’t produce RBCs and they’re small so the RBC count will be low along with the MCV. so the Mentzer's index is not as low, >13 Comparatively, In Thalassemia which is a disorder of Globin synthesis, RBC production is preserved, but the cells are much small and fragile. So the RBC count is normal with a low MCV. Thus the Mentzer's index is <11, This concept may be more helpful than memorizing numbers for Mentzer index.
It is also important to note that the test has a high specificity and low sensitivity. In a lot of cases, the Index would fall in between 11 and 13, such cases a peripheral blood smear and iron studies would help to differentiate Iron deficiency from Thalassemia.
2. Thalassemia minor.
ReplyDeleteLow MCV (nl 80 - 100) rules out 4. Absence of transfusion rules out 2. So we have to distinguish between 1 &2.
In IDA, the RBC count is usually less due to decreased production. Whereas in thalassemias, RBC are produced but hemoglobin is defective.
Use Mentzer index.
The Mentzer index is used to differentiate iron deficiency anemia from beta thalassemia.
It is calculated from the results of a complete blood count. If the quotient of the mean corpuscular volume divided by the red blood cell count is less than 13, thalassemia is more likely. If the result is greater than 13, then iron-deficiency anemia is more likely.
Here it is 55/4.5 < 13
This test helps in differentiating iron deficiency from Thalassemia. In Iron deficiency, the marrow can’t produce RBCs and they’re small so the RBC count will be low along with the MCV. so the Mentzer's index is not as low, >13 Comparatively, In Thalassemia which is a disorder of Globin synthesis, RBC production is preserved, but the cells are much small and fragile. So the RBC count is normal with a low MCV. Thus the Mentzer's index is <11, This concept may be more helpful than memorizing numbers for Mentzer index.
It is also important to note that the test has a high specificity and low sensitivity. In a lot of cases, the Index would fall in between 11 and 13, such cases a peripheral blood smear and iron studies would help to differentiate Iron deficiency from Thalassemia.