Hb Variant (hemoglobin Variant) Analysis

The doctor will order this test when there is an abnormal test results when CBC is conducted or an abnormal blood smear that suggests abnormalities in hemoglobin.

There are a few common hemoglobin variants. The hemoglobin variant analysis test helps identify these variants. The tests results are useful to manage the condition.

• Hemoglobin S variant is seen in people with sickle cell anemia
• Hemoglobin C Variant causes a mild case of hemolytic anemia and to an extent enlargement of spleen. This is usually a milder form of disease
• Hemoglobin E leads to hemolytic anemia, microcytic blood cells and enlargement of spleen. When this variant is present along with other mutation like that of the beta thalassemia trait, it could lead to moderate to severe symptoms

Haemoglobin Variant Analysis is a test that helps diagnose haemoglobin abnormalities including thalassemia.

Other names: Hemoglobin Evaluation, Haemoglobinopathy Evaluation

Hemoglobinopathies are inherited blood disorders due to abnormal forms of hemoglobin. Hemoglobin is an important component of the blood and contains of two parts – one is the iron carrying heme and four amino acids that form the globin portion. The globin chains have different names; alpha, beta, gamma and delta.

• Normal types of Hemoglobin are HbA (this is the most abundant type and makes up about 95-98% of Hb found in adults). HbA contains two alpha protein chains and two beta protein chains.
• HbA2 contains two alpha and two delta chains and makes up about 2-3% of Hb
• HbF is present in less than 1% Hb and has two alpha and two gamma chains.

Any changes in the globin chains lead to blood disorders. The changes in the globin structure affects the structure of hemoglobin, production rate, stability and how it behaves. The most common disorder is called as Thalassemia.

The laboratory will interpret the results with a lot of care. A hematopathologist will interpret the test report. Your doctor will help interpret the test result for you and may also order additional tests like Iron Studies to arrive at a diagnosis.

High performance liquid chromatography (HPLC) is a fast and accurate method for determining the presence and for quantitation of various type of normal Hb and common abnormal Hb variants, including but not limited to Hb S, C, E, D and beta - thalassemia. The diagnosis of these abnormal Hb variants should be confirmed by DNA an alysis. The method used has a limited role in the diagnosis of alpha thalassemia.

Slight elevation in hemoglobin A2 may also occur in hyperthyroidism or when there is deficiency of vitamin B12 or folate and this should be distinguished from inherited elevation of HbA2 in beta-thalassemia trait.

In adults, the percentage of normal haemoglobin variants are as below.

• Hemoglobin A -     96-98%
• Hemoglobin A2 -     3-3.5%
• Hemoglobin F -     0-2%
• Hemoglobin S -     0%
• Hemoglobin D -     0%
• Hemoglobin C -     0%
• Hemoglobin (E+A2) -     0%
• Peak2 -     0-10%
• Unknown identified peak -     0-2%
• Non-specific peaks -     0-10%

• It is ordered when a CBC count or a blood smear test comes abnormal
• The doctor will order this test when you exhibit signs of anemia like fatigue, pallor, lack of energy, weakness etc.
• Used to diagnose Hemoglobin Abnormalities and Thalassemia
• People with thalassemia have inherited mutations that affects the amount and type of hemoglobin in the blood, thus leading to decreased amount of normal hemoglobin. Since less oxygen is delivered, the red blood cells do not function properly. The two broad types of thalassemia are alpha and beta thalassemia and depending on the number of mutations and depending on the state of mutation (dominant or recessive), there are different subtypes.