Distinguishing Alpha Thalassemia Trait from Iron Deficiency Anemia

Diagnostic Criteria

The British Society of Gastroenterology recommends Hb electrophoresis in patients with microcytosis and normal iron studies, particularly if there is an appropriate ethnic background, to distinguish alpha thalassemia trait from iron deficiency anemia 1, 2
A low Mentzer index (<13) is characteristic of thalassemia trait, and is calculated as MCV/RBC count, with MCV reduced out of proportion to the level of anemia 1, 2
RDW ≤14% is indicative of thalassemia trait, unlike iron deficiency which shows RDW >14% 3, 4
Iron deficiency anemia is characterized by low MCV with low RBC count, high RDW (>14%), and low ferritin (<15-30 μg/L) 1, 2, 3, 4

MCV <80 fL with normal or slightly reduced hemoglobin is suggestive of alpha thalassemia trait 3, 4
Increased RBC count (the numerator in the Mentzer calculation) is also characteristic of alpha thalassemia trait 3, 4
Normal HbA2 levels are seen in alpha-thalassemia trait, unlike beta-thalassemia trait which shows elevated HbA2 >3.5% 1, 2