Hemoglobin electrophoresis is a

blood test A blood test is a laboratory analysis performed on a blood sample that is usually extracted from a vein in the arm using a hypodermic needle, or via fingerprick. Multiple tests for specific blood components, such as a glucose test or a cholester ...

that can detect different types of

hemoglobin Hemoglobin (haemoglobin BrE) (from the Greek word αἷμα, ''haîma'' 'blood' + Latin ''globus'' 'ball, sphere' + ''-in'') (), abbreviated Hb or Hgb, is the iron-containing oxygen-transport metalloprotein present in red blood cells (erythrocyte ...

. The test can detect hemoglobin S, the form associated with

sickle cell disease Sickle cell disease (SCD) is a group of blood disorders typically inherited from a person's parents. The most common type is known as sickle cell anaemia. It results in an abnormality in the oxygen-carrying protein haemoglobin found in red blo ...

, as well as other abnormal types of hemoglobin, such as

hemoglobin C Hemoglobin C (abbreviated as HbC) is an abnormal hemoglobin in which glutamic acid residue at the 6th position of the β-globin chain is replaced with a lysine residue due to a point mutation in the '' HBB'' gene. People with one copy of the gene ...

. It can also be used to investigate

thalassemia Thalassemias are inherited blood disorders characterized by decreased hemoglobin production. Symptoms depend on the type and can vary from none to severe. Often there is mild to severe anemia (low red blood cells or hemoglobin). Anemia can result ...

s, which are disorders caused by defective hemoglobin production.

Procedure

The test uses the principles of

gel electrophoresis Gel electrophoresis is a method for separation and analysis of biomacromolecules ( DNA, RNA, proteins, etc.) and their fragments, based on their size and charge. It is used in clinical chemistry to separate proteins by charge or size (IEF ...

to separate out the various types of hemoglobin and is a type of native gel electrophoresis. After the sample has been treated to release the hemoglobin from the red cells, it is introduced into a porous gel (usually made of

agarose Agarose is a heteropolysaccharide, generally extracted from certain red seaweed. It is a linear polymer made up of the repeating unit of agarobiose, which is a disaccharide made up of D-galactose and 3,6-anhydro-L-galactopyranose. Agarose is o ...

cellulose acetate In biochemistry, cellulose acetate refers to any acetate ester of cellulose, usually cellulose diacetate. It was first prepared in 1865. A bioplastic, cellulose acetate is used as a film base in photography, as a component in some coatings, and ...

) and subjected to an

electrical field An electric field (sometimes E-field) is the physical field that surrounds electrically charged particles and exerts force on all other charged particles in the field, either attracting or repelling them. It also refers to the physical field fo ...

, most commonly in an

alkaline In chemistry, an alkali (; from ar, القلوي, al-qaly, lit=ashes of the saltwort) is a base (chemistry), basic, ionic compound, ionic salt (chemistry), salt of an alkali metal or an alkaline earth metal. An alkali can also be defined as ...

medium. Different hemoglobins have different charges, and according to those charges, they move at different speeds in the gel and eventually form discrete bands (see electrophoretic migration patterns). A

quality control Quality control (QC) is a process by which entities review the quality of all factors involved in production. ISO 9000 defines quality control as "a part of quality management focused on fulfilling quality requirements". This approach places ...

sample containing hemoglobins A, F, S, and C is run along with the patient sample to aid in identifying the different bands. The relative amounts of each type of hemoglobin can be estimated by measuring the optical density of the bands, though this method is not reliable for hemoglobins that are present in low quantities. Because hemoglobins exhibit different migration patterns depending on the pH level, testing the same sample at both an acid and an alkaline pH can help to identify some abnormal hemoglobins that would otherwise be impossible to distinguish from others.

Clinical significance

Adult human blood normally contains three types of hemoglobin:

hemoglobin A Hemoglobin A (HbA), also known as adult hemoglobin, hemoglobin A1 or α2β2, is the most common human hemoglobin tetramer, accounting for over 97% of the total red blood cell hemoglobin. Hemoglobin is an oxygen-binding protein, found in erythrocyte ...

, which makes up approximately 95% of the total; hemoglobin A₂, which accounts for less than 3.5%; and a minute amount of

hemoglobin F Fetal hemoglobin, or foetal haemoglobin (also hemoglobin F, HbF, or α2γ2) is the main oxygen carrier protein in the human fetus. Hemoglobin F is found in fetal red blood cells, and is involved in transporting oxygen from the mother's bloodstream ...

. If abnormal hemoglobin variants such as hemoglobin S (which occurs in

), C or E are present, they will appear as unexpected bands on electrophoresis (provided they do not migrate to the same place as other hemoglobins). Hemoglobin electrophoresis can also be used to investigate

s, which are caused by decreased production of subunits of the hemoglobin molecule. Hemoglobin A₂ levels are typically elevated in

beta-thalassemia minor Beta thalassemias (β thalassemias) are a group of inherited blood disorders. They are forms of thalassemia caused by reduced or absent synthesis of the beta chains of hemoglobin that result in variable outcomes ranging from severe anemia to cl ...

and hemoglobin F may be slightly increased. In

beta-thalassemia major Beta thalassemias (β thalassemias) are a group of inherited blood disorders. They are forms of thalassemia caused by reduced or absent synthesis of the beta chains of hemoglobin that result in variable outcomes ranging from severe anemia to cl ...

, hemoglobin A is decreased (or in some cases absent) and hemoglobin F is markedly elevated; A2 levels are variable. In

hemoglobin H disease Hemoglobin H disease is a type of alpha thalassemia caused by impaired production of three of the four alpha globins, coded by genes HBA1 and HBA2. See also * Hemoglobin Barts Hemoglobin Barts, abbreviated Hb Barts, is an abnormal type of hemog ...

, a form of

alpha-thalassemia Alpha-thalassemia (α-thalassemia, α-thalassaemia) is a form of thalassemia involving the genes ''HBA1'' and ''HBA2''. Thalassemias are a group of inherited blood conditions which result in the impaired production of hemoglobin, the molecule t ...

, an abnormal band of hemoglobin H can be detected, and sometimes a band of

Hemoglobin Barts Hemoglobin Barts, abbreviated Hb Barts, is an abnormal type of hemoglobin that consists of four gamma globins. It is moderately insoluble, and therefore accumulates in the red blood cells. Hb Barts has an extremely high affinity for oxygen, so it ...

; but in the milder

alpha-thalassemia trait Alpha-thalassemia (α-thalassemia, α-thalassaemia) is a form of thalassemia involving the genes ''HBA1'' and ''HBA2''. Thalassemias are a group of Genetic disorder, inherited Blood diseases, blood conditions which result in the impaired productio ...

, electrophoresis results are effectively normal.

History

Linus Pauling Linus Carl Pauling (; February 28, 1901August 19, 1994) was an American chemist, biochemist, chemical engineer, peace activist, author, and educator. He published more than 1,200 papers and books, of which about 850 dealt with scientific top ...

is credited with the invention of hemoglobin electrophoresis in 1949. Newer alternatives to conventional hemoglobin electrophoresis include

isoelectric focusing Isoelectric focusing (IEF), also known as electrofocusing, is a technique for separating different molecules by differences in their isoelectric point (pI). It is a type of zone electrophoresis usually performed on proteins in a gel that takes ad ...

capillary zone electrophoresis Capillary electrophoresis (CE) is a family of electrokinetic separation methods performed in submillimeter diameter capillaries and in micro- and nanofluidic channels. Very often, CE refers to capillary zone electrophoresis (CZE), but other electr ...

, and

high-performance liquid chromatography High-performance liquid chromatography (HPLC), formerly referred to as high-pressure liquid chromatography, is a technique in analytical chemistry used to separate, identify, and quantify each component in a mixture. It relies on pumps to pa ...

References

Blood tests {{Hematology blood tests