How Is Thalassemia Diagnosed?

Thalassemia is diagnosed using blood tests, including a complete blood count (CBC) and special hemoglobin studies.

• A CBC provides information about the amount of hemoglobin and the different kinds of blood cells, such as red blood cells, in a sample of blood. People with thalassemia have fewer red blood cells than normal and less hemoglobin than normal in their blood. Carriers of the trait may have slightly small red blood cells as their only sign.
• Hemoglobin studies measure the types of hemoglobin in a blood sample.

Cooley’s anemia is usually diagnosed in early childhood because of signs and symptoms, including severe anemia. Some people with milder forms of thalassemia may be diagnosed after a routine blood test shows that they have anemia. Doctors suspect thalassemia if a child has anemia and is a member of an ethnic group that is at risk for thalassemia.

To distinguish anemia caused by iron deficiency from anemia caused by thalassemia, tests of the amount of iron in the blood may be done. Iron-deficiency anemia occurs because the body doesn’t have enough iron for making hemoglobin. The anemia in thalassemia occurs not because of a lack of iron, but because of a problem with either the alpha globin chain or the beta globin chain of hemoglobin. Iron supplements do nothing to improve the anemia of thalassemia, because missing iron is not the problem.

Family genetic studies are also helpful in diagnosing thalassemia. This involves taking a family history and doing blood tests on family members.

Prenatal testing can determine if an unborn baby has thalassemia and how severe it is likely to be.