Rosh Internal Medicine Boost Practice Exam

Which laboratory study is essential for confirming a diagnosis of thalassemia?

1. Bone marrow biopsy

2. Hemoglobin electrophoresis

3. Iron studies

4. Peripheral smear

The correct answer is: Hemoglobin electrophoresis

Hemoglobin electrophoresis is essential for confirming a diagnosis of thalassemia because it quantitatively measures the different types of hemoglobin present in the blood. Thalassemia is characterized by reduced or absent synthesis of one of the globin chains, either alpha or beta, leading to an abnormal hemoglobin pattern. In patients with alpha thalassemia, the hemoglobin types—such as H hemoglobin (β4) or the presence of excess alpha chains—can be detected. Likewise, in beta thalassemia, the hemoglobin electrophoresis can reveal an increase in fetal hemoglobin (HbF) and the presence of HbA2 (α2δ2) due to the lack of beta chains. Understanding the specific hemoglobin variant distribution allows clinicians to not only confirm the diagnosis but also to differentiate between the types and understand the severity of the thalassemia. Other laboratory studies, while helpful in the overall assessment of hematological status and differential diagnosis, do not specifically confirm thalassemia. For instance, a bone marrow biopsy could provide information about hematopoiesis but is not routinely performed for diagnosing thalassemia. Iron studies are important for evaluating iron deficiency anemia but would not specifically diagnose