Microcytic Anemia: Iron Deficiency vs Thalassemia
Low MCV (below 80 fL) with anemia is the classic microcytic picture. The two leading causes need different workups.
Iron deficiency anemia
- Ferritin low (< 12-30 ng/mL) is diagnostic of absent iron stores.
- TIBC elevated, transferrin saturation low (< 16%), iron low.
- RDW usually high (anisocytosis), Mentzer index (MCV/RBC) above 13.
Thalassemia trait
- Ferritin and iron studies typically normal or only mildly reduced.
- RDW normal or near normal, Mentzer index below 13.
- Platelets often elevated; target cells and basophilic stippling on the film.
- Confirm with hemoglobin electrophoresis (elevated HbA2 in beta-thalassemia trait; alpha-thalassemia trait appears with a normal pattern).
Mixed picture
In inflammation, ferritin can be normal despite true deficiency because it is an acute-phase protein; a low transferrin saturation with elevated CRP is consistent with the anemia of chronic disease versus combined deficiency.
Key checks
MCV, RBC, hemoglobin, RDW, ferritin, TIBC, iron, transferrin saturation, and, when indicated, hemoglobin electrophoresis.