Generality
Electrophoresis is a technique used in the laboratory analysis that exploits the molecular mass and the electric charge of proteins, to evaluate their quantity and quality . In particular, this exam allows the separation of proteins into five fractions : albumin, alpha 1 globulin, alpha 2 globulin, beta globulin and gamma globulin . The alteration of the relationship between these types of proteins is indicative of some pathological conditions. Electrophoresis can be performed on blood serum samples, urine or other biological fluids, such as liquor (cerebrospinal fluid).
Also called protein electrophoresis or protidogramma, this test is carried out by adopting a very particular method: an electric field is applied to the sample, thanks to which the proteins "group" by type. In fact, each of the proteins that analyze electrophoresis has its own molecular mass and an electric charge, which allows them to respond to the stress, supplied by the direct current, in a characteristic way. Under normal conditions, for example, the first expected peak - higher and narrower - in the electrophoretic path corresponds to albumin .
In more practical terms, electrophoresis is an analysis used to determine:
- The presence of abnormal proteins;
- The absence of normal proteins;
- If a group of proteins is present in smaller or greater quantities than the norm.
The electrophoresis can be requested by the doctor as part of the control exams (routine analysis) or of the diagnostic procedure, that is in the case in which other laboratory analyzes have shown alterations and it is necessary to deepen or confirm a clinical suspicion.
What's this
Electrophoresis is a laboratory analysis that provides important information about the amount of proteins present in blood serum or in other biological samples and, for each fraction, reveals if there are any anomalies in terms of quality. This is possible by applying an electric field, exploiting the electrophoretic mobility of proteins; the migration of these macromolecules is influenced by their mass, size, charge and shape.
In particular, the test allows the separation of proteins into five groups : albumin, alpha 1 globulin, alpha 2, beta and gamma .
The result of the electrophoresis allows to examine the concentration of these parameters: the possible alteration of the relationship between these groups of proteins is observed during some pathological states. Therefore, electrophoresis is useful in confirming a diagnosis and, once the disease has been ascertained, in following the patient in the follow-up .
Electrophoresis: on which samples can be performed?
The biological samples to which electrophoresis can be applied are mainly:
- Serum : seroprotein electrophoresis or serum protein electrophoresis;
- Urine : urinary electrophoresis or electrophoresis of urinary proteins;
- Liquor (cerebrospinal fluid) : electrophoresis of liquor proteins (note: liquor is the fluid that permeates and protects the brain, spinal cord, cranial nerves and spinal roots).
Electrophoresis: what is measured
Plasma proteins are very important indicators: any alterations in their concentrations can signal the presence of numerous diseases.
With electrophoresis it is possible to separate the following proteins in the sample:
- Albumin ;
- Alpha 1 globulins ;
- Alpha 2 globulins ;
- Beta globulins ;
- Gamma globulins .
At present, many laboratories carry out a 6-band separation, ie with the separation of beta globulins in two fractions:
- Beta 1 globulins ;
- Beta 2 globulins .
Did you know that…
In the laboratory, electrophoresis is one of the most widely used techniques for analyzing the qualitative and quantitative composition of proteins. This separation method is based on the different migration speed of electrically charged particles, through a solution and a support medium, under the influence of an electric field .
Albumin is the most abundant serum protein, and one of the most important in the body. This is synthesized by the liver and is contained above all in interstitial liquids and in plasma, where it represents, by itself, about half of the circulating proteins. Albumin carries out various functions, including the correct management of osmotic pressure and the transport of substances, such as bilirubin.
Alpha 1 and 2 globulins primarily perform lipid, blood fat and hormone transport functions. Beta globulins also carry the substances present in the blood; among the most well-known proteins of this group are transferrin (used to transport iron) and beta-2 microglobulin. Gamma globulins have, instead, mainly an antibody function.
Some plasma proteins are produced by the liver (such as albumin), while others are released into the blood from cells that belong to the immune system (gamma globulin).
Read more: Plasma Proteins - Functions and Features »Electrophoresis: basic principle
Introduction : in general, electrophoresis is a separation method based on the different migration speed of electrically charged particles, through a solution and a porous and inert support medium (such as paper, agarose gel or cellulose acetate sheet), under the impulse of an electric field. Many molecules of biological interest (amino acids, peptides, proteins, DNA and RNA) possess ionizable groups in their structure, therefore, at a suitable pH value, these are present in solution as electrically charged species. Under the influence of an electric field these charged molecules migrate towards the cathode or the anode, depending on whether they have a positive charge ( cation ) or negative charge ( anions ).
Electrophoresis is a method that allows the separation of macromolecules and, in particular, proteins based on their:
- Molecular mass ;
- Electric charge .
When placed in a basic environment, the proteins behave as acids: the COOH group of the various amino acids that make up the structure of the macromolecule, dissociates into COO– (negative particle) and H + (positive ion). The proteins are loaded, therefore, as a whole in a negative sense and their electrophoretic mobility goes from the negative pole (cathode) to the positive one, that is towards the anode (since the negative charges exceed the positive ones).
Returning to the examination, the patient's sample - containing a mixture of proteins (eg serum proteins) - is placed on an electrophoretic strip, ie the support for migration .
The separation in five bands is obtained through the application of an electric field, generated by a direct current, which allows the different protein fractions to migrate based on their mass and their electric charge.
The result - called ELECTROPHORETIC TRACK - is made up of various peaks and curves, to which the protein fractions correspond, divided by type and quantity, present in the liquid under examination:
- Normally, the first peak, higher and narrower, is that of ALBUMINA ;
- Next, we observe the peaks of the GLOBULINES, much lower than albumin.
The increase or decrease in amplitude and intensity of the peaks that form in the path indicate a greater or lesser presence of proteins in each category.
Did you know that…
Transthyretin was previously called prealbumin due to its greater electrophoretic mobility compared to albumin, which allows it to migrate to a more anodic position.
For further information: Prealbumin - What is it »Why it runs
What is Electrophoresis for?
Electrophoresis is used to diagnose or monitor diseases that have among their clinical findings an alteration of protein concentrations in plasma, urine or other biological samples.
This anomaly can occur, for example, in the event of:
- Diseases of the liver and kidneys ;
- Infections or inflammations ;
- Multiple myeloma ;
- Multiple sclerosis .
Electrophoresis: when is the examination prescribed?
INTRODUCTION : the dosage of total proteins in the blood - proteinemia - and of albumin - albuminemia - is normally included in the control panels, therefore it is frequently used in the evaluation of a person's health status . In routine analysis, the alteration of these parameters can be considered a BELL OF ALARM and can induce to deepen the clinical picture, especially if the patient shows a particular symptomatology.
PROTEIN IN SERUM electrophoresis can be prescribed:
- In the case in which other laboratory tests provide an abnormal result, in terms of absence or smaller and greater quantity of plasma proteins with respect to the norm;
- When the presence of:
- Inflammation in progress;
- Infection;
- Autoimmune disease;
- nephropathy;
- liver disease;
- Diseases characterized by the production of a monoclonal component, that is antibodies with the same identical chemical structure, such as:
- Multiple myeloma and its variants;
- Waldenström's macroglobulinemia;
- Amyloidosis.
When in the urine there is a high concentration of proteins, instead, the doctor can request the execution of the electrophoresis of URINARY PROTEINS . The examination allows to determine the source of the alteration, confirming or supporting the diagnosis.
PROTEIN DEL LIQUOR electrophoresis can be prescribed when the diagnosis of multiple sclerosis is suspected. In this case, the electrophoretic pattern that is determined is characteristic, since it highlights the presence of the so-called oligoclonal bands, not normally present in the electrophoresis of serum proteins.
Once the disease is diagnosed, electrophoresis can be performed at regular intervals to:
- Monitor the disease over time, then follow its course (follow-up);
- Check the effectiveness of the therapeutic protocol .
Normal values
In an adult in good health, the normal concentration of total protein in the blood is 6.4-8.3 grams per deciliter of plasma (g / dl).
Albumin (Seroprotein Electrophoresis)
Albumin constitutes 59-69% of total plasma proteins.
- Reference value Albumin: 3.6-4.9 g / dl
Alpha 1 globulin
Alpha-1 globulins make up 2.0-3.5% of total plasma proteins.
- Reference value Alpha 1 globulin : 0.2-0.4 g / dl
Alpha 2 globulins
Alpha-2 globulins account for 6-11% of total plasma proteins.
- Reference value Alpha 2 globulins : 0.4-0.8 g / dl
Beta globulins
Beta globulins make up 6-12% of total plasma proteins.
- Beta globulin reference value : 0.6-1 g / dl
Gamma globulins
Gamma globulins make up 9-20% of total plasma proteins.
- Reference value Gamma globulin : 0.9-1.4 g / dl
Note : the reference interval of the exam may vary slightly depending on age, sex and instrumentation used in the analysis laboratory. For this reason, it is preferable to consult the ranges listed directly on the report. It should also be remembered that the results of the analyzes must be assessed as a whole by the general practitioner who knows the patient's medical history.
High Values - Causes
Serum electrophoresis: what causes the increase in values?
ALBUMIN
The finding with electrophoresis of an increase in serum albumin is frequent during morbid states that subtract water from the body and lead to the appearance of dehydration, including:
- Persistent vomiting and diarrhea;
- Extensive burns;
- Excessive sweating;
- Addison's disease;
- Diabetic coma.
In the electrophoretic tracing, a concentration of albumin higher than the norm could be indicative of:
- Sarcoidosis (systemic inflammatory disease);
- Buerger's disease or tromboangioite obliterans (disease affecting blood vessels and arteries).
ALFA 1 GLOBULINE
Alpha 1 globulins are increased in the following cases:
- Inflammatory process or infection in progress;
- Heart attack;
- Taking the contraceptive pill;
- Pregnancy.
ALFA 2 GLOBULINE
High values of alpha 2 globulins may indicate the presence of:
- Kidney diseases;
- Inflammation or ongoing infection;
- Heart attack;
- Diabetes;
- Down syndrome;
- Some malignant tumors.
BETA GLOBULINE
The increase in beta globulins in the electrophoretic trace is indicative of:
- High cholesterol in the blood (hypercholesterolemia);
- Iron deficiency anemia;
- Some cases of multiple myeloma;
- Pregnancy.
GLOBULINE RANGE
In electrophoresis, the increase in polyclonal gamma globulins may be associated with:
- Chronic inflammatory diseases;
- Some diseases of the immune system;
- Rheumatoid arthritis;
- Systemic lupus erythematosus;
- Chronic liver diseases (such as hepatitis and cirrhosis);
- Acute and chronic infections.
High values of monoclonal gamma globulins may indicate, instead, the presence of:
- Some tumors;
- Multiple myeloma;
- lymphoma;
- Waldenström's macroglobulinemia.
To identify which gamma globulin is present in the monoclonal band in an electrophoretic pattern, it is possible to proceed with an immunofixation.
Urine electrophoresis
A significant increase in protein in the urine by electrophoresis can indicate malfunction of the glomeruli and renal tubules .
Liquor electrophoresis
If the electrophoresis results proteins not normally present in the cerebrospinal fluid or they are increased, there could be an inflammation, an infection or other diseases of the nervous system .
The finding of oligoclonal bands in the electrophoretic tracing is indicative of multiple sclerosis .
Low Values - Causes
Serum electrophoresis: what causes protein reduction?
ALBUMIN
A reduction in albumin in the electrophoretic tracing can be caused by all those conditions characterized by:
- Malnutrition (in particular: protein deficiency due to reduced dietary intake);
- Malabsorption secondary to: enteropathies, celiac disease, Crohn's disease, protein intolerances;
- Increased catabolism : severe inflammation, febrile states, cachexia, neoplasms, hyperthyroidism, hypercortisolism, etc.
The albumin peaks also decrease following pathologies that affect the liver (the ability to synthesis is lacking) and the kidney (increases elimination).
The concentration of albumin detected with serum electrophoresis can decrease, in particular, when they are established:
- Liver cirrhosis (is the most common cause);
- Acute and chronic hepatitis;
- Genetic anomalies (synthesis of defective albumins);
- Kidney disease (especially nephrotic syndrome and glomerulonephritis).
The finding of a low albumin with electrophoresis is also observed in pregnancy for:
- Hormonal modifications that alter the vascular permeability and the functionality of numerous organs of the pregnant woman;
- Increased use of proteins by the fetus.
ALFA 1 GLOBULINE
Alpha 1 globulins are reduced to electrophoresis in the presence of:
- Severe liver disease;
- Congenital emphysema;
- Kidney diseases.
ALFA 2 GLOBULINE
Low values of alpha 2 globulins may be indicative of:
- Malnutrition;
- Severe liver disease;
- Hemolysis.
BETA GLOBULINE
A reduced concentration of beta globulins in the electrophoresis trace may indicate:
- Malnutrition;
- Liver cirrhosis.
GLOBULINE RANGE
Low gamma globulin values can indicate the presence of various diseases of the immune system.
Urine electrophoresis
Normally, a small concentration of protein in urine is found with electrophoresis. Therefore, this result does not indicate the presence of certain diseases.
Liquor electrophoresis
Under normal conditions, the concentration of total proteins in the liquor is very low. The finding of values reduced to electrophoresis does not correlate, therefore, to a particular pathological significance.
How it is performed
Electrophoresis: what the exam consists of
- Whey electrophoresis (blood test) : to obtain the electrophoretic tracing on the serum it is necessary to undergo a simple blood sample from the vein of an arm. Subsequently, the serum is obtained by separating the fraction containing the cells from the liquid one.
- Urinary protein electrophoresis (urinalysis) : it is necessary to collect a small amount of urine in a special sterile container. Based on the indications of the doctor and the laboratory, the sample can be collected without a precise timing ( random ) or within 24 hours .
- Liquor electrophoresis (analysis of cerebrospinal fluid) : requires the collection of a small quantity of liquor, through the insertion of a needle, inside the spinal cavity ( lumbar puncture ).
Preparation
Electrophoresis: is preparation required?
- Prior to blood sampling, some laboratories may require you to observe a fast of at least 10-12 hours. During this time a small quantity of water is allowed.
- Electrophoresis can be performed on urine collected at a certain time of the day (random) or during the 24 hours, so it is necessary to obtain the appropriate sterile containers beforehand.
- As far as liquor electrophoresis is concerned, however, no special preparation is required.
What can alter the outcome of the exam?
Some medicines can affect the outcome of electrophoresis, so it is advisable to report any ongoing therapies to the doctor. Medications that can alter the clinical finding include oral contraceptives, anabolic steroids, androgens, growth hormones, insulin and antibiotics.
Other factors that may influence the exam include:
- Hyperlipidemia (presence of many fats in the blood);
- Administration of large amounts of intravenous fluids;
- Vegetarian diet;
- Hemolyzed samples (if electrophoresis is performed on serum).
Interpretation of Results
The electrophoresis pathway is evaluated in combination with the results of other analyzes and provides information on the patient's health status.
The decrease or increase compared to the standard of proteins in serum, urine or liquor electrophoresis shows the presence of different diseases, identified on the basis of the parameter affected by the alteration.
It must always be remembered that the reference values can change from one laboratory to another. Therefore, it is essential to consult your primary care physician or a reference specialist for reading and interpreting the results.
