Serum protein electrophoresis.
A laboratory test that examines specific proteins in the blood called globulins.
Technique in which the blood serum is placed into a gel, or into liquid in a capillary tube, and exposed to an electric current to separate the serum protein components into five major fractions by size and electrical charge: serum albumin, alpha-1 globulins, alpha-2 globulins, beta globulins, and gamma globulins.
Fractions include:
Albumin
Albumin – Alpha-1 Interzone
Alpha-1 Zone
Alpha-1 – Alpha-2 Interzone
Alpha-2 Zone
Alpha-2 – Beta Interzone
Beta Zone
Beta-Gamma Interzone
Gamma Zone
Albumin is the major fraction in a normal SPEP.
A fall of 30% in albumin is necessary before the decrease shows on electrophoresis.
Usually a single band is seen.
Heterozygous individuals may produce bisalbuminemia – two equally staining bands, the product of two genes, and some variants give rise to a wide band or two bands of unequal intensity but none of these variants is associated with disease.
Absence of albumin is known as analbuminaemia and is rare.
A decreased level of albumin is common in many diseases, including: liver disease, malnutrition, malabsorption, protein-losing nephropathy and enteropathy.
Albumin – Alpha-1 Interzone is due to alpha-1 lipoprotein (High density lipoprotein – HDL).
Decrease in Albumin – Alpha-1 Interzone occurs in severe inflammation, acute hepatitis, and cirrhosis.
Nephrotic syndrome can lead to decrease in albumin level, due to its loss in the urine through a damaged leaky glomerulus.
An increase appears in severe alcoholics and in women during pregnancy and in puberty.
The high levels of AFP that may result in a sharp band between the albumin and the alpha-1 zone.
Orosomucoid and antitrypsin migrate together but orosmucoid stains poorly so alpha 1 antitrypsin (AAT) constitutes most of the alpha-1 band.
Alpha-1 antitrypsin associated with a decreased band is seen in the deficiency state.
Alpha-1 antitrypsin is decreased in the nephrotic syndrome and absence could indicate possible alpha 1-antitrypsin deficiency.
Alpha-1 antitrypsin eventually leads to emphysema from unregulated neutrophil elastase activity in the lung tissue.
The alpha-1 fraction does not disappear in alpha 1-antitrypsin deficiency because other proteins, including alpha-lipoprotein and orosomucoid, also migrate there.
Alpha-1 fraction is a positive acute phase reactant, and Alpha-1 antitrypsin is increased in acute inflammation.
Bence Jones protein may bind to and retard the alpha-1 band.
Alpha-1 – Alpha-2 Interzone associated with 2 bands representing alpha-1 antichymotrypsin and vitamin D binding protein.
These bands fuse and intensify in early inflammation due to an increase in alpha-1 antichymotrypsin, an acute phase protein.
Alpha-2 zone consists principally of alpha-2 macroglobulin and haptoglobin.
There are typically low levels in hemolytic anaemia.
Haptoglobin is a suicide molecule which binds with free hemoglobin released from red blood cells.
Haptoglobin-hemoglobin complexes are rapidly removed by phagocytes.
Haptoglobin is raised as part of the acute phase response, resulting in a typical elevation in the alpha-2 zone during inflammation.
A normal alpha-2 and an elevated alpha-1 zone is seen in hepatic metastasis and cirrhosis.
Haptoglobin/haemaglobin complexes migrate more cathodally than haptoglobin as seen in the alpha-2 – beta interzone. This is typically seen as a broadening of the alpha-2 zone.
Alpha-2 macroglobulin may be elevated in children and the elderly.
Alpha-2 macroglobulin is markedly raised with glomerular protein loss, as in nephrotic syndrome, due to its large size, it cannot pass through glomeruli, while other lower-molecular weight proteins are lost.
Enhanced synthesis of Alpha-2 macroglobulin accounts for its absolute increase in nephrotic syndrome.
Alpha-2 macroglobulin is mildly elevated early in the course of diabetic nephropathy.
Beta lipoprotein levels are seen in type II hypercholesterolaemia, hypertriglyceridemia, and in the nephrotic syndrome.
Beta Zone: the transf2242in and beta-lipoprotein (LDL) comprises the beta-1.
Increased beta-1 protein due to the increased level of free transf2242in is typical of iron deficiency anemia, pregnancy, and estrogen therapy.
Increased beta-1 protein due to LDL elevation occurs in hypercholesterolemia.
Decreased beta-1 protein occurs in acute or chronic inflammation.
Beta-2-Complement protein 3.
It is raised in the acute phase response.
Depression of C3 occurs in autoimmune disorders as the complement system is activated and the C3 becomes bound to immune complexes and removed from serum.
Fibrinogen, a beta-2 protein, is found in normal plasma but absent in normal serum.
Beta-Gamma Interzone-C-Reactive Protein is found in between the beta and gamma zones producing beta/gamma fusion.
IgA migrates in the region between the beta and gamma zones also causing a beta/gamma fusion in patients with cirrhosis, respiratory infection, skin disease, or rheumatoid arthritis (increased IgA).
Gamma Zone-The immunoglobulins (IgA, IgM, IgG, IgE and IgD) are the only proteins present in the normal gamma region, but note that immunoglobulins may be found in the alpha and beta zones.
If the gamma zone shows a spike it could indicate a monoclonal production of a single immunoglobulin while a broad enlargement indicates polyclonal immunoglobulin production.
Gel electrophoresis is performed to detect and confirm monoclonal immunoglobulins.
Typically, a monoclonal gammopathy is malignant or clonal in origin.
Multiple myeloma monoclonal gammopathy being the most common cause of IgA and IgG spikes. chronic lymphatic leukemia are not uncommon and usually give rise to IgM paraproteins.
Up to 8% of healthy elderly patients may have a monoclonal spike.
Waldenstrom’s macroglobulinemia (IgM), monoclonal gammopathy of undetermined significance (MGUS), amyloidosis, plasma cell leukemia and solitary plasmacytomas also produce an M-spike.
A broad elevation in the gamma zone indicates a polyclonal gammopathy, which typically indicates a non-neoplastic condition.
The most common causes of polyclonal hypergammaglobulinemia detected by electrophoresis are severe infection, chronic liver disease, rheumatoid arthritis, systemic lupus erythematosus and other connective tissue diseases.
Hypogammaglobulinemia is identifiable as a decrease in the gamma zone.
Hypogammaglobulinemia is normal in infants.
Hypogammaglobulinemia is found in patients with X-linked agammaglobulinemia.
IgA deficiency occurs in 1:500 of the population, as is suggested by a pallor in the gamma zone.
Lysozyme may be seen as a band in the slowest gamma in myelomonocytic leukemia in which it is released from tumour cells.
Fibrinogen will be seen in the fast gamma region.