Evaluation for Thalassemia Trait

Initial Laboratory Assessment

Mean Corpuscular Volume (MCV) is typically low in thalassemia trait, with values often below the 5th percentile for age 1
Red Blood Cell (RBC) count is often normal or elevated in thalassemia trait, in contrast to iron deficiency anemia where it is typically low 1
Red Blood Cell Distribution Width (RDW) is a critical differentiating factor: RDW ≤14.0% suggests thalassemia trait, while RDW >14.0% suggests iron deficiency anemia 1

Important: HbA2 measurement should be performed after iron deficiency has been corrected, as iron deficiency can falsely lower HbA2 levels 2, 1

Serum ferritin should be measured to rule out concurrent iron deficiency, which can mask thalassemia trait characteristics 3, 1
If iron deficiency is present (ferritin below reference range), iron replacement therapy should be provided before final assessment for thalassemia trait 3, 1

Concurrent iron deficiency can mask the typical laboratory findings of thalassemia trait, particularly HbA2 elevation in beta-thalassemia trait 2, 1
Lead poisoning, anemia of chronic inflammation, and sickle cell trait can present with similar red cell indices and must be excluded 1

Peripheral blood smear examination is essential to confirm the size, shape, and color of red blood cells, which is a critical step in the diagnostic approach for thalassemia, as recommended by the National Comprehensive Cancer Network 4
The reticulocyte count is an important parameter to distinguish between decreased production and increased destruction or loss of red blood cells, which can help in the diagnosis of thalassemia, according to the Journal of the National Comprehensive Cancer Network 4

The CDC recommends that in pregnant women with suspected thalassemia trait and concurrent iron deficiency, persistent mild anemia despite adequate iron therapy should prompt evaluation for beta‑thalassemia minor or sickle‑cell trait. 5

The CDC advises that individuals of African, Mediterranean, or Southeast Asian ancestry who exhibit mild anemia that does not respond to iron supplementation should be assessed for beta‑thalassemia minor or sickle‑cell trait. 5