Proteinogram (study of protein fractions) – biochemical analysis aimed at determining the percentage of albumins and globulins in plasma. Proteinogram can be carried out in combination with total blood protein, prothrombin time, transaminases. The proteinogram is used in the diagnosis and dynamic monitoring of the course of treatment of systemic connective tissue diseases, acute and chronic inflammatory processes, blood diseases, conditions associated with immunodeficiency. Venous blood serum is used for protein fractionation. The analysis is performed by electrophoresis. During the study, 5 fractions were isolated: albumin, alpha-1-globulin, alpha-2-globulin, beta-globulin, gamma-globulin. Determine their quantitative content (in g / l) and the ratio (in %%). The duration of the study is from 1 to 3 working days.
Most of the blood proteins are represented by albumins – their plasma content varies from 55 to 65%. The remaining part of the proteins is accounted for by the globulin fraction. Synthesis of albumins, alpha- and beta-globulins occurs in liver cells. A significant proportion of beta- and gamma-globulins are produced in the bone marrow and lymphatic tissue. If the percentage of protein components deviates from normal values, dysproteinemia develops. At the same time, the level of total protein may remain unchanged.
The main role of serum albumin is the preservation of colloidal osmotic plasma pressure at a constant level, the distribution of water between blood vessels and the interstitial space. Albumins are carriers of bile pigments, bilirubin, drugs and some hormones.
Globulins are divided into 4 main fractions. Alpha-1-globulin is largely represented by alpha-1-antitrypsin, which performs the function of inhibiting protease – trypsin, chymotrypsin and elastase. The composition of alpha-1-globulin includes alpha-acid glycoprotein, involved in the formation of new fibrils in the inflammatory zone, and proteins that transport fats and hormones.
Alpha-2-globulin includes acute-phase proteins: alpha-2-macroglobulin, haptoglobin, ceruloplasmin and the transport protein apolipoprotein B. Alpha-2-macroglobulin is a protein modulator of inflammatory and immune reactions, participates in the blood clotting system, is a nonspecific marker of liver fibrosis. Haptoglobin forms a compound with free hemoglobin during the destruction of erythrocytes, thereby preventing its excretion from the body; the role of this globulin in activating lymphocytes in the focus of inflammation has been proven. Ceruloplasmin is a protein characterized by a high antioxidant capacity. Its leading role is the oxidation of divalent iron into safe trivalent iron. Ceruloplasmin contains 90% of the body’s total copper.
Beta-globulin mainly consists of an iron transporter protein, transferrin. Globulin also includes beta-lipoproteins that transport cholesterol and phospholipids; immunoglobulins and complement components involved in the formation of humoral and cellular immunity. Gamma globulin consists of a set of immunoglobulins – IgG, IgM, IgA, IgE. These compounds are antibodies that are mostly responsible for humoral immunity. Their main function is to protect the body from infectious agents.
Proteinogram is used in rheumatology to diagnose systemic connective tissue diseases, determine the degree of disease activity and the effectiveness of therapy. Immunologists and infectious disease specialists use the results of the analysis to assess the ability of the immune system to adequately respond to exogenous and endogenous antigens, the severity of the inflammatory process. In gastroenterology, protein fractionation in the blood is carried out to diagnose and monitor liver and intestinal diseases, determine the level of liver failure and the severity of the syndrome of impaired intestinal absorption.
Proteinogram is prescribed during the second stage of a comprehensive examination based on the results of identified deviations in clinical and biochemical parameters. The analysis is indicated for pathological bone fractures, increased calcium in the blood, anemia. Such symptoms may indicate the development of osteoporosis associated with the accumulation of paraprotein in the bones with myeloma. A proteinogram is prescribed for edema and pronounced proteinuria to exclude nephrotic syndrome due to pathology of the hepatorenal system, the development of hypo- and dysproteinemia.
Proteinogram is indicated for unexplained weakness, prolonged fever, frequent colds. These symptoms appear due to a decrease in the level of globulin fraction in plasma and the development of an immunodeficiency condition. The analysis is carried out for the purpose of differential diagnosis of liver and kidney diseases, congenital insufficiency of individual protein fractions, endocrine diseases.
After an X-ray examination with contrast, hemodialysis and plasmapheresis procedures, a one-week delay in conducting the study is required.
Preparation and blood collection
Preparation for proteinogram should begin in advance. A few weeks before the planned analysis, cholesterol-lowering medications are canceled. Approximately three days before the study, you should not engage in heavy physical work and drink alcoholic beverages. The break between blood collection and the last meal should be at least 8-10 hours. 1 hour before the immediate delivery of the analysis, you can not smoke. Blood is taken in the morning.
Blood from the peripheral vein is taken with a disposable syringe or using a vacuum system – vacutiner. A test tube with blood is marked, information about the patient is entered into a regular or electronic journal. The marked containers are handed over to the courier in a special container for transportation to the medical laboratory. There are many ways of fractionation of proteins in the blood: precipitation with neutral salts, immunological, sedimentation analysis, chromography, gel filtration and electrophoretic. At the moment, protein electrophoresis on plates with agar gel has become the most widespread.
The principle of the method is based on the separation of protein macromolecules that differ in molecular weight, configuration and electric charge. The test material is introduced into the hole located at the edge of the gel. A charged dye is added to the well and an electric current is started. Small molecules in mass and configuration move faster and further. Gradually, all the material with the dye is distributed in zones along the entire length and reaches the end of the plate. Each zone has its own protein fraction. By the saturation of the staining of the stripes, the concentration of protein molecules is judged.
Proteinogram is a high-tech and time-consuming analysis that requires special training of a laboratory technician. The duration of the study is from 1 to 3 days, depending on the equipment and workload of the laboratory.
Normal values of proteinogram
Normal values of protein fractions may differ slightly in different laboratories. Therefore, the result obtained must be compared with the indicators indicated on the form. The unit of measurement is % (percentage). In adults, reference values have the following ranges: albumin – 55-65, alpha-1-globulin – 2.5-5, alpha-2-globulin – 6-12, beta-globulin – 8-15, gamma-globulin – 11-21%. According to the results of the analysis, the ratio of albumins to globulins is determined, the so-called albumin-globulin coefficient. Normally, a healthy person has a coefficient of 1.5-2.3.
In children, the level of globulins is slightly lower than in adults. During the third trimester of pregnancy, there is a physiological decrease in albumins and gamma globulins, and the fractions of alpha-1, alpha-2 and beta globulins, on the contrary, increase. The decrease in albumin is associated with its increased use for fetal growth and development. A decrease in the level of gamma globulins is a compensatory reaction that prevents the development of an immune reaction of the expectant mother to foreign fetal tissues.
Raising the level
Albumin. An increase in albumins in the blood is possible in conditions accompanied by fluid loss: vomiting, diarrhea, prolonged fever with profuse sweating. The reason for the relative increase in albumin in the blood in these cases is a decrease in the mass of circulating blood. The concentration of albumin increases with extensive burns and severe injuries accompanied by shock. The genesis of protein enhancement is the same.
Alpha-1-globulin. The indicator increases with acute inflammation (bronchopneumonia, cholecystitis), rheumatic and infectious diseases. The reason is an increase in the level of alpha-1-antitrypsin and alpha-1 acid glycoprotein, which are produced by the body to simulate a local immune response. The concentration of alpha-1-globulin increases with cirrhosis of the liver, lymphogranulomatosis, pregnancy with fetal pathology.
Alpha-2-globulin. The fraction level increases with nephrotic syndrome. This is due to the development of a compensatory mechanism, expressed in accelerated protein synthesis as a response to its increased excretion by the kidneys. An increase in the concentration of alpha-2-globulin is noted in chronic liver diseases, myocardial infarction, systemic connective tissue diseases, neoplastic processes. The reason for the increase in the indicator is an increase in the production of alpha-2-macroglobulin, haptoglobin and ceruloplasmin, which are involved in immune and inflammatory reactions.
Beta-globulin. An increase in the level of beta-globulin occurs in acute inflammatory diseases, glomerulonephritis, rheumatoid arthritis. The reason is the increased formation of immunoglobulins and activation of the complementary system involved in cellular and humoral immunity. The growth of beta-globulin in iron deficiency anemia is associated with accelerated synthesis of transferrin in response to a decrease in the concentration of iron in the body. The level of beta-globulin increases with hereditary and acquired hyperlipoproteinemia. This is due to the increased load on transport proteins – beta-lipoproteins, which are carriers of cholesterol and phospholipids.
Gamma globulin. An increase in the gamma globulin fraction is noted in chronic infections, worm infestations, dermatomyositis, scleroderma. The reason is the formation of B-cell immunity, accompanied by an increase in the production of immunoglobulins of class G and E. The level of the indicator increases with Waldenstrom’s macroglobulinemia, myeloma. This is due to the synthesis of a huge mass of pathological proteins.
Lowering the level
Albumin. A decrease in the concentration of albumin in the blood accompanies diabetic nephropathy, nephrotic syndrome. This is due to increased protein excretion in the urine through damaged renal tubules. The causes of hypoalbuminemia in hepatitis and cirrhosis of the liver are inhibition of albumin synthesis by hepatocytes. A decrease in albumin levels is noted in enterocolitis and pancreatitis. In these conditions, the absorption of proteins coming from food slows down. Neoplastic processes, hyperthyroidism, prolonged therapy with corticosteroids reduce the concentration of albumin due to the rapid destruction of protein compounds.
Alpha-1-globulin. A decrease in the level of alpha-1-globulin is observed in patients with severe chronic obstructive pulmonary disease, bronchial asthma, emphysema. The cause is congenital deficiency of alpha-1-antitrypsin. The fraction level decreases in acute viral hepatitis due to massive liver damage and violation of its protein-synthetic function.
Alpha-2-globulin. A decrease in the level of alpha-2-globulin is observed in diseases accompanied by intravascular hemolysis or increased release of hemoglobin. These include autoimmune hemolytic anemia, malaria, posttransfusion hemolysis. This is due to the fact that the level of haptoglobin is rapidly depleted due to binding to highly toxic free hemoglobin. The concentration of alpha-2-globulin decreases with pancreatitis, burns, treatment with alteplase and streptokinase. The reason is the rapid removal of alpha-2-macroglobulin with proteolytic enzymes.
Beta-globulin. A drop in the concentration of beta-globulin in the blood occurs with cirrhosis of the liver due to the inhibition of the synthesis of this protein by liver cells. A decrease in the indicator is noted in conditions associated with iron overload, for example, with frequent blood transfusions or hemachromatosis. The reason is the increased consumption of transferrin protein involved in the transport of iron to the bone marrow and liver. A decrease in the level of beta-globulin in the blood is found in malignant tumors, extensive burns and injuries, due to the rapid breakdown of protein in the body.
Gamma globulin. A reduced level of gamma globulin is noted in hereditary and acquired immunodeficiency conditions, such as Bruton’s disease, lymphosarcoma, lymphogranulomatosis. In these conditions, gamma globulins are not produced at all, or their synthesis in the body sharply decreases.
Treatment of abnormalities
The results of a blood test for protein fractions are very difficult to interpret. They cannot be used for self-diagnosis and treatment. An accurate diagnosis can only be made by a doctor in conjunction with the patient’s complaints and anamnesis data, other analyses and instrumental examination methods. After determining the cause and type of dysproteinemia, the specialist determines the treatment tactics and recommendations that must be strictly followed.