In the article, we will consider how the leukocyte formula is calculated.
Leukocyte formula (aka leukogram) - the percentage ratio of different types of leukocytes, which is determined by counting them under a microscope in a stained blood smear.
A blood test for the level of leukocytes can be done in almost every medical institution. The result of it will be a form issued to the patient, indicating the obtained indicators and the limits of the norm, characteristic of his age category.
What is a leukocyte count in a blood smear and what is it for?
Definition, general information
Leukocytes, like other blood cells, are formed in the bone marrow. Their main function is to fight infection and respond to tissue damage.
Unlike erythrocytes, whose population is homogeneous,There are five types of white blood cells that differ in their function and appearance: basophils, neutrophils, eosinophils, monocytes, and lymphocytes.
Leukocytes are formed from brain stem cells of the head. They do not last long, so they are constantly updated. The production of white blood cells in the bone marrow rises in response to any tissue injury, part of the normal inflammatory response. Different types of leukocytes have their own functions, but they can interact in a coordinated way, contacting with the use of certain components - cytokines.
For a long time, manual counting of the leukocyte formula was carried out.
High accuracy of results
Modern analyzers make it possible to analyze blood in automatic mode with higher accuracy (a specialist looks at one hundred or two hundred cells, while a device looks at several thousand). When the apparatus for calculating the leukocyte formula determines atypical cellular forms or determines significant deviations from the reference values, the leukocyte formula can be supplemented with a microscopic analysis of a blood smear, which makes it possible to diagnose a number of pathologies, such as infectious mononucleosis, to establish the severity of the infection process, to determine the type of diagnosed atypical cells in leukemia. Human assistance is needed only when errors are identified, in order to double-check the result of counting the leukocyte formula.
This approach greatly simplifies the procedure, but, unfortunately, not all laboratories have the necessary equipment at present.
Methods for calculating the leukocyte formula
Depending on the density, leukocytes are unevenly distributed in smears: close to the edges, along the periphery - eosinophils, basophils and neutrophils; closer to the center - lymphocytes and monocytes.
When calculating the leukocyte formula, use the Schilling method or the Filippchenko method.
The Schilling method determines the number of leukocytes in four areas of the smear. This is a four field method. A total of one hundred to two hundred cells are counted in a smear.
The essence of the Filippchenko leukocyte count method is that the smear is mentally divided into three parts, such as initial, final and average (three-field method). Count in a straight line from one edge of the stroke across it to the other. The same number of cells is counted in each part. Only one hundred to two hundred leukocytes are counted. The cells found are entered into the Egorov grid - a special table of differential counting. For a more convenient and quick determination of the leukocyte formula, a special eleven-key counter is used. Techniques for counting leukocyte formula are constantly being improved.
Carrying out an analysis to determine the leukocyte formula
The use of leukocyte count in a blood smear for accurate diagnosis of pathologies is quite difficult, since the ratio of particles is often similar in various inflammatory processes in the body. Typically, the information obtained is used to track the dynamics of the disease and the degree of effectiveness of therapy. Preparation for blood sampling for research is not too difficult - for a personyou just need to refuse food at least four hours before the analysis, and on the eve it is advisable to avoid strong emotional and physical exertion.
Venous blood serves as the material for determining the leukocyte formula. Before the procedure, the laboratory assistant pinches the patient's forearm with a special strap, then inserts a thin needle into the vein in the elbow bend, through which blood enters directly into the test tube. Then a drop of the resulting material is transferred to a glass plate in order to calculate the ratio of leukocytes and their number using a microscope. If the clinic has modern equipment, the particles are considered a special analyzer, and the need for human intervention arises only when the result reflects strong deviations from the norm or the presence of anomalous particles. The values obtained can be evaluated by the attending physician.
Clinical significance
Leukogram in clinical practice is very important, because with any changes in the human body, the percentage concentration of some types of white blood cells decreases or increases due to a decrease or increase in others to one degree or another. According to the leukocyte formula, one can draw conclusions about the course of the pathological process, the occurrence of complications and make a prognosis of the outcome of the disease. Leukogram information must also be compared with the clinical symptoms of the pathology.
What is the interpretation of a blood test with a leukocyte formula?
There are several criteria by which the condition of the blood andthe proportion of white blood cells will be evaluated by a specialist.
Shift the leukocyte formula to the right or left
Of particular importance is the study of neutrophils in a blood smear. The doctor draws a conclusion about the rate of development or the presence of the disease based not only on their number. Also, the age of the cells also plays an important role, for example, the predominance of young neutrophils over more mature ones, and vice versa. The result of the analysis is therefore called a shift, because the entry of the blood formula follows a certain order - first, young types of neutrophils are taken into account, then more mature cells in ascending order. When an imbalance appears, therefore, there is a shift in indicators in one direction or another. If the number of young neutrophils is increased, they speak of a shift to the left of the leukocyte formula, which may indicate the presence of various pathological processes in the body. He talks about tissue necrotic processes, inflammation, infectious diseases, gas or food poisoning, as well as the consequences of taking various kinds of medicines. However, a shift to the left does not necessarily indicate pathology - there may be a temporary cellular imbalance after heavy physical exertion, which quickly returns to normal. The opposite situation - a shift to the right of the leukocyte formula - indicates the predominance of mature neutrophils in the blood. Such a distribution of blood white cells may indicate a deficiency of vitamin B12, radiation sickness, kidney and liver diseases. A shift to the right is seen in people who have had a recent blood transfusion.
What do high numbers mean?
If the number of neutrophils increases when counting the leukocyte formula in a blood test, this may indicate a large number of diseases and various specific human conditions. Such an effect can be observed with the appearance of infectious pathologies, including fungal origin (for example, candidiasis), an increase in blood glucose levels in diabetes, rheumatism, the presence of cancerous tumors of various localization, mercury or lead poisoning. A high content of neutrophils in the blood is also observed after severe pain, physical and emotional stress, as well as under the influence of extremely high or low temperatures.
Exceeding the norm of lymphocytes
If the norm of lymphocytes is exceeded, we can talk about the presence of an infectious disease, blood pathologies, arsenic or lead poisoning, as well as the result of using a number of medicines. After the patient has suffered an infectious disease, the content of monocytes in his blood increases. In addition, this condition of the blood is observed in people with malignant tumors, autoimmune diseases, and in case of poisoning with phosphorus and tetrachloroethane.
It is interesting to note that leukocytes, before dying, can transmit a specific signal to neighboring cells about danger. This is the conclusion reached by Australian scientists who analyzed the behavior of cells using a special device,taking hundreds of pictures per second. An increased content of eosinophils is noted with an allergic reaction to antibiotics, drugs for convulsive conditions and tuberculosis, parasitic invasion, a number of diseases of the lungs and skin, and an acute course of infectious pathology. Tuberculosis, chickenpox, influenza - such diseases can cause an increase in the number of basophils in the blood.
In addition, the concentration of this type of white blood cells increases with ulcerative colitis, allergic reactions, as a result of high sensitivity to certain foods, and may also indicate the presence of cancerous tumors in the body.
Decreased rates and their meaning
If the concentration of neutrophils is significantly reduced when calculating the leukocyte formula in a smear, a specialist can diagnose any infectious disease (tuberculosis, typhoid fever), excessive sensitivity to drugs (anti-inflammatory and antihistamines, antibiotics), anaphylactic shock and anemia.
Lymphocytes have reduced levels in the leukocyte formula in acute inflammatory processes, immunodeficiency states of the body, systemic lupus erythematosus and kidney failure. In addition, an increase in the concentration of particles is characteristic of people who are exposed to x-ray radiation. Also, no less serious reasons can reduce the number of monocytes in a blood test. These include aplastic anemia, pyogenicinfections and oncohematological pathologies. In addition, the effect in the form of a decrease in the content of monocytes can be caused by the use of certain drugs and a state of severe shock.
Decreased eosinophil concentration
You can diagnose the very beginning of the inflammatory process with a strong decrease in the concentration of eosinophils. This also happens when the body is poisoned with heavy metals and the nature of the purulent infection is serious. Severe stress, pregnancy and the ovulation period can become natural causes for a decrease in the content of basophils in the blood. Pathological causes include Cushing's syndrome and infectious diseases. The leukocyte formula allows a specialist to diagnose and monitor the degree of effectiveness of therapy for allergic reactions, various blood diseases, inflammations and other pathologies.
Conclusion
With such advantages as high accuracy, reproducibility and objectivity, the study can rightfully be considered one of the most revealing methods of blood analysis. The procedure cannot be performed at home, so you should contact the laboratory to calculate the leukocyte count.
We looked at how the leukocyte blood formula is calculated.
