Distinguishing Iron Deficiency from Thalassemia Trait

Initial Evaluation

A systematic approach combining CBC parameters with serum ferritin and hemoglobin electrophoresis is recommended to distinguish iron deficiency from thalassemia trait, as both present with microcytic anemia but have different iron stores and hemoglobin patterns 1, 2
The minimum essential tests include complete blood count with MCV, MCH, and RBC count 1, 2
Red cell distribution width (RDW) is a useful test, with elevated RDW strongly suggesting iron deficiency 2, 3
Serum ferritin is the most specific test for iron deficiency in the absence of inflammation 4, 5

Serum ferritin <30 μg/L strongly indicates iron deficiency 1, 4, 5
High RDW indicates variable red cell sizes due to progressive iron depletion 2, 3
Elevated RBC count with low MCV suggests thalassemia trait 6
MCV disproportionately low relative to degree of anemia is characteristic of thalassemia trait 4, 5
Elevated HbA2 >3.5% on hemoglobin electrophoresis is definitive for beta-thalassemia trait 6

Check serum ferritin first, as ferritin <30 μg/L strongly indicates iron deficiency 1, 4, 5
Evaluate RBC count and RDW, as elevated RBC count with low MCV suggests thalassemia trait 6
Order hemoglobin electrophoresis when microcytosis is present with normal iron studies, or when there is an appropriate ethnic background (Mediterranean, Asian, African descent) 4, 5

Both conditions can coexist, and iron deficiency can mask thalassemia trait by lowering HbA2 levels below the diagnostic threshold of 3.5% 6
Inflammation affects ferritin interpretation, and ferritin up to 100 μg/L may still be consistent with iron deficiency in inflammatory conditions 1, 4, 5

For confirmed iron deficiency, initiate therapeutic iron supplementation (3-6 mg/kg/day elemental iron) and investigate underlying cause (GI blood loss, menstrual losses, malabsorption) 4, 5, 6
For confirmed thalassemia trait, provide genetic counseling and recommend partner screening if family planning is relevant, and avoid chronic iron therapy beyond correction of any coexisting deficiency 6