Total protein in the blood is the main biochemical indicator reflecting amino acid metabolism in the human body. Total protein test is usually carried out in combination with other biochemical parameters. Total protein test is informative in the diagnosis and monitoring of the course of kidney and liver diseases, metabolic disorders, oncopathology, infections, monitoring the effectiveness of therapy. Venous blood plasma is used for quantitative protein analysis. Most often, the determination of this indicator is carried out by the colorimetric method. The range of protein levels in the blood of a healthy adult ranges from 65 to 85 g/l. The duration of the study is no more than one working day.
Total protein in the blood is the total content of all types of proteins circulating in the plasma. The main fractions are albumins and globulins. Albumin is formed in the liver, its fraction is homogeneous in its structure and makes up about 60% of the total amount of proteins. Globulins are represented by a heterogeneous composition, are formed in the liver and reticuloendothelial system (lymphocytes and plasma cells). The concentration of total protein depends on the rate of its synthesis from amino acids.
The “extra” protein is not deposited in the body, so the proteins unused by the body are broken down to nitrogenous compounds, carbon dioxide and water. Ammonia is neutralized in the liver with the formation of urea and excreted by the kidneys with urine. Proteins involved in purine metabolism are converted into uric acid. The latter is excreted in urine and feces.
The main function of serum proteins is to preserve the body’s homeostasis by participating in various biochemical processes. Plasma proteins maintain the acid-base state of the blood, are part of blood clotting factors, thereby affecting the degree of its “fluidity”. The quantitative content of proteins in the blood determines the level of colloidal osmotic pressure, the distribution of water between the tissues of the body. Proteins in the blood perform a transport function by binding and transferring lipids, pigments, hormones, fragments of drugs to human tissues and organs. The globulin fraction of the protein performs a protective function. In response to the invasion of foreign agents, the body synthesizes immunoglobulins, antibodies, opsonins, etc.
Determination of the total protein level is carried out during routine biochemical screening. Surgeons and resuscitators use the indicator to evaluate the effectiveness of intensive therapy for shock conditions and dynamic monitoring of postoperative patients. In cardiology and nephrology, the results of the analysis for total protein help to determine the causes of edema, disorders of excretory kidney function. In hepatology and toxicology, repeated protein testing is carried out in order to monitor the course of treatment of liver failure.
Indications and contraindications
Total protein test is prescribed as part of the first stage of a comprehensive examination for the diagnosis of various diseases and pathological conditions. In case of subcutaneous hemorrhages, vomiting of “coffee grounds”, black stools, the analysis for total protein is carried out in combination with a coagulogram. These manifestations may indicate a decrease in the synthesis of proteins in the liver responsible for blood clotting. The study of total protein in the blood together with the determination of cholesterol and the daily loss of protein in the urine is carried out with a decrease in diuresis, the occurrence of edema in the face and lower legs in the morning. Such symptoms are characteristic of nephrotic syndrome – it is associated with excessive excretion of proteins by the kidneys, a decrease in oncotic (protein) pressure in the blood and, as a consequence, fluid retention in tissues.
Total protein test indicated for pain in the bones and lumbar region. Pain may signal a possible accumulation of pathological protein in the bone tissue and kidneys. The study of total protein is prescribed for significant weight loss, cachexia. Such symptoms may indicate signs of alimentary protein “starvation”, rapid protein breakdown in oncological diseases. The analysis is performed to monitor the effectiveness of treatment of liver and kidney failure, autoimmune and oncological diseases, diseases of the gastrointestinal tract and severe infections. There are no contraindications to the appointment of a blood test for total protein.
Preparation and blood collection
Blood should be donated in the morning from 8 a.m to 11 a.m. It is taken in the manipulation room from the veins of the ulnar fossa or hand. Blood plasma is used for the study.
In order for the results to be as accurate as possible, you should follow some rules. During the day before taking the analysis, you can not expose yourself to intense physical exertion. 8 hours before taking blood, it is necessary to stop eating, drink only clean water in a small amount. 30 minutes before the study, you should not smoke and expose yourself to stress.
A disposable syringe with a dry test tube or a modern vacuum system is used to take blood. The blood container is marked, the patient’s data is indicated and the information is entered into a log or an electronic database. The labeled test tube is placed in a special container and sent to the laboratory.
There are several ways to determine the total protein in the blood: azotometric, gravimetric, spectrophotometric, refractometric and colorimetric. The most common colorimetric method is the determination of protein by biuretic reaction. When copper sulfate is added to the blood serum, complex compounds are formed that turn the solution purple. The protein concentration is determined by the degree of intensity of staining of the solution.
As a rule, a day is enough to obtain the results of the study. In life-threatening conditions, an analysis can be carried out urgently for several hours to assess the severity of the disease and choose treatment tactics. In this case, a note “cito” is made on the referral form.
In children under 1 month, the level of total protein is at the level of 46-68 g/l, from 1 month to 1 year – 48-76 g /l, from 1 year to 15 years – 60-80 g/l. In adults, the concentration in the blood is 65-85 g / l. After the age of 65, the level of protein in the blood decreases by several units.
A physiological decrease in protein levels in the blood may be associated with intense physical exertion: the “construction” of new muscle tissue or increased protein catabolism during energy “starvation”. The level of protein in the blood increases briefly when the body moves from a horizontal position to a vertical one. A decrease in the concentration of protein in the blood is noted in vegetarians and those who want to lose weight quickly due to complete starvation or the use of a protein-free diet.
A relative physiological decrease in the concentration of protein in the blood is observed with increased sweating. This is especially necessary to take into account when staying in a hot climate. A sufficient amount of fluid allows you to avoid blood thickening and, as a result, the formation of blood clots. In the third trimester of pregnancy, the level of total protein decreases due to the active use of albumin for fetal development and growth. A drop in protein concentration during lactation is associated with an increased expenditure of amino acids for the synthesis of protein molecules of mother’s milk.
Increased blood levels
Frequent vomiting with intestinal obstruction, diabetes insipidus diabetes, diabetic ketoacidosis lead to dehydration of the body. The reason for the relative increase in protein in the blood in these cases is a decrease in the volume of circulating blood. The concentration of protein in the blood increases with acute and chronic infections, systemic connective tissue diseases (rheumatism, scleroderma, dermatomyositis). The causes of hyperproteinemia are the protective reaction of the body, which consists in the increased production of immune complexes and antibodies in response to exogenous and endogenous antigens.
Excessive content of total protein is noted in myeloma, Waldenstrom’s macroglobulinemia. In these cases, a huge amount of pathological proteins is produced in the body. The concentration of protein in the blood increases to 120-160 g / l. Hyperproteinemia accompanies the shock stage of burn disease, severe peritonitis. Its cause is dehydration of the body and activation of the immune system.
Decrease in blood levels
A decrease in the concentration of total protein in the blood accompanies liver diseases with manifestations of liver failure: hepatitis, cirrhosis, toxic lesions. The causes of hypoproteinemia in these cases are inhibition of protein synthesis. A drop in the level of protein in the blood is noted in the pathology of the small intestine and pancreas – in these diseases, the process of absorption of proteins coming from food is disrupted.
With glomerulonephritis, amyloidosis, diabetic kidney damage, a decrease in protein in the blood is associated with damage to the renal tubules and increased protein excretion in the urine. Malignant neoplasms, thyrotoxicosis, long-term treatment with corticosteroids reduce the concentration of protein. The reason for its decrease is the rapid breakdown of protein molecules.
The level of protein in the blood decreases with ascites, pleurisy and pericarditis. In these cases, proteins rush into the so-called “third spaces”, their presence is determined in effusion fluids. Hypoproteinemia accompanies injuries, extensive burns, postoperative and septic conditions. The reason for the decrease in protein in these conditions is the increased catabolism of proteins in the body.
Treatment of abnormalities
If there is a significant change in the level of total protein in the blood, you should immediately contact medical specialists to clarify the diagnosis. When diagnosing hypoproteinemia associated with insufficient protein intake from food, nephrotic syndrome, depletion of the body due to severe diseases, protein-rich foods are necessarily included in the diet. A large number of easily digestible proteins are found in chicken, turkey, rabbit, veal, fish, dairy products. Pork, lamb, fatty cottage cheese and sour cream should not be abused.
With increased fluid loss, it is necessary to consume clean drinking or mineral water in a timely manner and in sufficient quantities. Light physical education and “walking” in the fresh air improve metabolism and contribute to maintaining the necessary balance of proteins in the body.