What is B-Hemoglobin A2?
B-Hemoglobin A2 is one of several hemoglobin types that occur naturally in the blood. It normally constitutes a small proportion – around 2–3.5% – of the total hemoglobin in adults.
Hemoglobin A2 consists of two α-globin chains and two δ-globin chains (α₂δ₂), and is not pathological in itself. However, the level of HbA2 is very valuable as a diagnostic marker, especially when hereditary blood diseases such as β-thalassemia are suspected.
Included in the Hemoglobin Fractions test
The analysis of B-Hemoglobin A2 is one of several subcomponents of the broader B-Hemoglobin Fractions test. This test is used in the investigation of:
- Thalassemia and other hemoglobinopathies
- Sickle cell anemia and sickle cell trait
- Unexplained anemia or microcytosis
Together with analyses of, for example, HbF (fetal hemoglobin) and any deviant hemoglobins (e.g. HbS or HbE), the HbA2 value provides an overall picture of the patient's hemoglobin composition.
When is HbA2 analyzed?
The analysis is particularly recommended in the following cases:
- Suspected thalassemia minor/trait
- Microcytic anemia with normal iron levels
- Genetic investigation before pregnancy
- Elevated HbF or abnormal blood status
Sampling
The sample is taken via a regular blood sample in an EDTA tube (purple cap). The analysis is performed using advanced laboratory technology to separate and quantify different hemoglobin types.