Haemoglobin A2

Keywords: HbA2

Specimen:

5 mL blood in any anticoagulant.

Method:

Column chromatography, electrophoresis or HPLC, using lysate of washed red cells.

Reference Interval:

Consult laboratory. Approximate reference ranges provided below:

Hb A2 1.8-3.5%

Application:

Investigation of thalassaemias and haemoglobinopathies.

Interpretation:

HbA2 is usually raised in the ß thalassaemias, and in unstable haemoglobinopathies where the amino acid substitution is on the ß chain.

HbA2 may be reduced in the presence of iron deficiency; if thalassaemia is suspected in a patient with iron deficiency, the test should be repeated after iron replacement.

Acquired defects of HbA2 also exist. It may also be elevated in thyrotoxicosis and in megaloblastic anaemias. 

It may also be reduced in Lead poisoning, Anaemia of chronic disease, Sideroblastic anaemia, Hypothyroidism and in acquired HbH disease.

Reference:

Steinberg MH and Adams JG. Blood 1991; 78: 2165-2178.

Bain B. Haemoglobinopathy Diagnosis. 2nd Ed. 2006. Blackwell Science.