Biochemical blood analysis refers to complex laboratory tests. The tests included in its composition may vary depending on the goals set by the doctor. The obtained indicators are used to evaluate the work of many organs and systems, to identify metabolic disorders, water-electrolyte balance. Liver functions reflect ALT, AST, total bilirubin; kidney functions – urea, creatinine; metabolism – glucose, total protein, total cholesterol. Biochemical blood analysis is used in all areas of clinical practice, is carried out as part of screening examinations of various groups of patients, is indicated for diseases of the heart, blood vessels, blood, gastrointestinal tract, kidneys, hepatobiliary and endocrine systems, musculoskeletal system. The biomaterial for analysis is venous blood. Tests are performed using colorimetric, UV-kinetic and other methods. The results are prepared in 1 day.
The introduction of biochemical blood analysis into clinical practice took place several decades ago. The basis of this process was the rapid development of biochemistry and organic chemistry in general, the shift in the focus of research on the processes occurring in a living cell. Fundamental ideas about the components of the body’s biological fluids and the metabolic reactions occurring in them made it possible to associate changes in blood composition with certain diseases, metabolic disorders, functional shifts in the work of organs and systems. To date, in our country, biochemical analyses account for about 15-20% of the total flow of laboratory research. This indicator is growing every year, as the equipment of laboratories with reagents and equipment is improving, more economical and, at the same time, more sensitive and specific research methods are being developed.
The scope of application of biochemical blood analysis is very wide. The research is in demand in all areas of medical practice: in therapy, surgery, endocrinology, obstetrics, gynecology, nephrology, gastroenterology, pediatrics, etc. The main biological material used in laboratories is blood from veins. Its chemical composition provides the doctor with information about the functional state of practically all organs. The complex interpretation of indicators occupies one of the central places in the diagnosis of diseases, assessment of the dynamics of the condition of patients with various pathologies and physiological conditions (pregnancy, aging, intense physical activity).
A set of tests in a biochemical blood test is selected by a doctor individually, taking into account the clinical picture, patient complaints, and data from other examinations. The basic complex includes the determination of ALT, AST, total bilirubin, urea, creatinine, glucose, total protein, total cholesterol. These analyses allow us to evaluate the metabolic processes, the work of the liver, kidneys. Additionally, tests for albumin, myoglobin, transferrin, ferritin, OHSS, CRP, rheumatoid factor, ceruloplasmin, triglycerides, fructosamine, alkaline phosphatase, alpha-amylase, lipase, creatine kinase, lactate dehydrogenase, GGTP, as well as the determination of trace elements can be introduced. In some diseases, a biochemical blood test is the only objective method of diagnosis.
Most often, a biochemical blood test is prescribed to patients undergoing inpatient or outpatient treatment. The results are used to establish a diagnosis, track the dynamics of the disease, determine treatment tactics, including to address the need and possibility of surgical intervention. For preventive purposes, the study can be recommended to anyone, since its indicators allow us to assess the state of the body, the presence of abnormalities in the work of organs. As part of screening, pregnant women, the elderly, and patients from risk groups for the development of a particular disease are often referred to donate blood for biochemistry.
The list of tests that will be included in the biochemical blood test is set by the doctor. Indicators are conditionally divided into several groups, each of which is aimed at assessing a certain exchange process and organ system. With changes in protein metabolism, the biochemical blood test includes the study of the level of total protein, albumin, globulins. These tests are indicated for patients with infections, inflammatory, including autoimmune diseases, pathologies of the kidneys and liver, as well as patients in an acute condition. Fat metabolism is characterized by such indicators as total cholesterol and triglycerides. Tests are necessary for patients with cardiovascular pathologies, diseases related to metabolism. The study of carbohydrate metabolism – glucose, fructosamine and some other indicators is prescribed for disorders in the work of the endocrine glands. Determination of the level of trace elements is indicated for violations of the water-electrolyte balance, acid-base balance, pathologies of the kidneys, heart.
A biochemical blood test includes indicators that are markers of pathologies of a particular organ. In case of liver damage, “liver tests” are carried out – determination of total bilirubin, alkaline phosphatase, GGT, AST and ALT. The main markers of pancreatic damage are amylase and lipase, markers of kidney damage are creatinine and urea. Cardio-rheumatoid indicators include troponins, myoglobin, creatine kinase, creatine kinase-MV. In diseases of the musculoskeletal system, a study of vitamin D and calcium is shown. As a rule, the same indicator reflects the functioning of several organs or even systems, so the selection of blood biochemical tests is a task for a qualified specialist.
Thus, a biochemical blood test is one of the basic diagnostic tools in clinical practice. It allows you to cover a wide range of diseases and functional conditions, while it does not require large time and economic costs, in many laboratories the research procedure is automated. There are no special limitations of this research method. Conditionally, they include the fact that many physiological factors, such as emotional state, eating habits, physical activity, can affect the result, and eventually the diagnosis. To avoid this, it is important to comply with all the requirements of preparation for blood donation.
Preparation and blood collection
To perform a biochemical analysis, blood is taken from a vein. The sampling procedure is usually performed in the morning. In order for the research indicators to be informative, it is necessary to follow several rules of preparation for the delivery of biomaterial. Firstly, it is worth adjusting the diet a little – to withstand 8-12 hours of night hunger, to refrain from drinking strong tea and coffee the night before, to give up fatty foods and alcohol in 2 days. Secondly, during the day it is necessary to limit the impact of physical stress factors – overheating (saunas, baths), sports, hard physical labor. Two weeks before the analysis, it is necessary to inform the attending physician about the medications taken, if necessary, they will be temporarily canceled. If any therapeutic procedures are planned on the day of the study, then they should be performed after blood donation. Half an hour before the procedure, you should refrain from smoking, avoid emotional stress, excessive physical activity.
After sampling, the blood is sent to the laboratory. Before the study, a serum is obtained from it – a yellowish transparent liquid from which the shaped elements and coagulation factors are removed. The method of investigation depends on the compound being determined, the most commonly used photocolorimetric and kinetic methods. The essence of photocolorimetry is that a reagent is added to the biomaterial sample, which forms colored complexes with the compound under study. After that, the optical density of the resulting mixture is measured, and the final indicator is calculated on its basis. Kinetic research methods are based on measuring the rate of a chemical reaction after the introduction of a reagent. The obtained value is used to determine the concentration of the compound under study. Despite the fact that the biochemical blood test includes a large number of indicators, the research procedures are automated (or semi-automated) and take no more than 1 working day.
The interpretation of the results of a biochemical blood test is based on a comparison of the obtained indicators with the values of the norm. Usually they are indicated in the form issued by the laboratory, depend on the research methods used, reagents and equipment used. Reference values for some tests are determined by age and/or gender:
* glucose – 4.1-5.9 mmol/l (children – 2.8-5.6 mmol/l);
* total bilirubin – 3.4-20.5 mmol/l (from 2 weeks);
* AST – no more than 31 Units/l for women, no more than 37 Units/l for men (children – no more than 47-48 units/l);
* ALT – no more than 34 Units/l for women, no more than 45 Units/l for men (children – no more than 39-54 units/l);
* total cholesterol – 3.2-5.6 mmol/l (children – 2.9-5.2 mmol/l);
* total protein – 64-83 g/l (children – 42-80 g/l);
* creatinine – 50-98 mmol/l for women, 64-111 mmol/l for men (children – 30-92 mmol/l);
* urea – 2.1-7.1 mmol/l (children – 1.4-6.4 mmol/l).
Physiological changes in the indicators of biochemical blood analysis occur during pregnancy, during breastfeeding, during recovery periods after intense physical exertion and emotional stress, after drinking alcoholic beverages, smoking, hypothermia or overheating. Also, dietary peculiarities can affect the results: overeating, abuse of fatty and spicy dishes, diets, lack of proteins, fats, vitamins or trace elements in the diet, etc.
Deviations from the norm
Biochemical blood analysis is in demand in almost all areas of clinical practice. Its indicators allow the doctor to judge the functional state of organs and systems, the peculiarities of metabolism, water-electrolyte balance, acid-base balance. The study is used for screening, diagnosis and monitoring of diseases. If one or more indicators do not correspond to the norm, then for the establishment of the cause of the deviation and the appointment of treatment, it is necessary to consult the doctor who sent for the study. Most often they are a therapist, gastroenterologist, endocrinologist, cardiologist, gynecologist.