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Leukocyte formula

The leukocyte formula is the percentage of the various forms of leukocytes in the blood, counted in a stained smear. It is subject to significant individual fluctuations (table 1). For a correct understanding of the shifts occurring in the blood, it is necessary to take into account not only percentage (relative), but also absolute values ​​(the content of each type of leukocytes in 1 mm 3 of blood). For this, the percentage of these cells is multiplied by the total number of blood leukocytes without two zeros. For example: the number of leukocytes in 1 mm 3 of blood - 6500, monocytes - 7%. The absolute number of monocytes in 1 mm 3 of blood is 7X65 = 455. The content of one type of white blood cells (see) may vary independently of the others. Thus, when bone marrow is inhibited, the absolute number of neutrophils decreases, and lymphocytes may remain unchanged, but their percentage increases. This will be relative lymphocytosis. For example: in typhoid fever, the number of leukocytes can be reduced to 3000 in 1 mm 3 , and lymphocytes can be 50%. Meanwhile, the absolute number of lymphocytes here is 50X30 = 1500, i.e. there is no absolute lymphocytosis.

Shifts in the leukocyte formula may depend on the redistribution of leukocytes in the vascular bed or on changes in the activity of the blood-forming organs . With the accelerated regeneration of cells, mainly neutrophils, the number of stab cells increases in the blood, young, immature forms are found - metamyelocytes, myelocytes. Such a change in leukocyte formula (characteristic, in particular, for inflammatory processes) is called a neutrophil shift to the left (the numbers on the left side of the record increase).

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Changes in leukocyte formula cannot be considered in isolation from the overall clinical picture. For example, for infections caused by coccal flora, neutrophilic leukocytosis with a shift to the left and eosinopenia is typical, for typhoid-paratyphoid diseases, influenza virus, and brucellosis , a picture of bone marrow depression with neutropenia and relative lymphocytosis is characteristic. However, an increase in the number of neutrophils in the case of viral flu may indicate not only recovery, but also a complication of the disease with a bacterial infection. When counting leukocyte formula, attention should also be paid to pathological changes in leukocytes: the appearance of large (“toxic”) grain in neutrophils, indicating severe intoxication in a patient, degenerative changes — vacuolation of cytoplasm and nuclei, pycnosis (shrinkage) of nuclei, etc. In the same smear take into account changes in red blood cells (see).
limits of normal oscillations of various forms of white blood cells

Leukocyte formula - the percentage of certain types of leukocytes in the blood. Leukocyte formulas make up as many leukocytes as possible in a stained dry blood smear, but not less than 200. It makes it possible to evaluate the functional state of those different hematopoietic tissues that are supplied to the blood by certain types of leukocytes. Leukocyte formula is subject to significant fluctuations in healthy people. In practice, leukocyte formula of human blood proposed by V. Schilling (table 1) is used most often.

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For a correct understanding of the real ratios of individual forms of leukocytes, it is necessary to know their total number in 1 mm 3 of blood and the percentage indicators of the number of leukocytes translate into absolute numbers. The number of leukocytes of individual species can vary independently of each other, and therefore it is necessary to distinguish their relative and absolute increase and decrease. For example, in lymphocytic leukemia, both the relative and absolute number of lymphocytes increases; the relative number of neutrophils remains low, and their absolute number may increase.

There are also two types of shift: regenerative and degenerative. The first is to increase the number of young people and, together with them, band-core with a corresponding decrease in segmented ones. This shift indicates a “rejuvenation” of white blood as a result of increased bone marrow activity and increased neutrophil loss. The degenerative shift is to increase only one form - band. At the same time, the total number of leukocytes is not increased, but normally or even reduced. This shift indicates inhibition of bone marrow function.

For a visual representation of the absolute amounts and ratios of individual forms of leukocytes in 1 mm 3 of blood, a graphical depiction of the leukocyte formula — the so-called leukocyte profile (Fig. 1) was proposed. The following figures are taken as the norm for an adult: neutrophils 3000–5500, lymphocytes 1200–2000, monocytes 200–600, eosinophils 100–250, basophils 0–80, and the total number of leukocytes 4000–8000. Connecting in each column the points set in the places corresponding to the absolute number of one or another type of white blood cells, we get a broken line, which is a leukocyte profile.


Fig. 1. Leukocyte profile: 1 - normal; 2 - with prolonged malaria, characterized by a profile with a truncated neutrophil apex; B — basophils; E - eosinophils; H - neutrophils; L - lymphocytes; M - monocytes. The rectangles mark the boundaries of the norm for absolute quantities of this type of white blood cells.

Normally, all points fall inside the rectangles. The exiting of any point of the profile beyond the limits of the norm indicates an increase or decrease in the absolute number of this type of white blood cells. The normal leukocyte profile in an adult is pointed, with the highest point in the neutrophil column and steep descent to the lymphocyte column. According to the leukocyte profile, it is possible to establish the true functional hyperplasia of various departments of the hematopoietic apparatus.

For a more complete description of the age composition of neutrophils, Sh. D. Moshkovsky suggests expressing their average age composition in a fraction, in which the numerator is the sum of percentages of myelocytes (M), metamyelocytes (S) and band (F), and the denominator is the total percentage of all neutrophils (H ):
[M + S + P] / H
Normally, this nuclear index is 0.05. With an increase in the total percentage of young neutrophils (M, U, P), for example, up to 40, the nuclear index can reach 0.5. See also Leukocytes.