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Anisocytosis of erythrocytes (red blood cells) is an indicator that reflects the width of their distribution. This measure is referred to in the analysis results as RDW. Previously, the Price-Jones curve was used to determine anisocytosis, which was quite difficult to draw.
Modern laboratory diagnostics practically does not use this curve, since the visual assessment of a blood smear under a microscope is associated with many errors. Hardware research in this regard is much more accurate and informative, provided that the devices work correctly. Therefore, the definition of anisocytosis in modern medicine is a task that falls on the analyzing device, and not on the laboratory assistant.
The rate of erythrocytes in the blood
Historically, both doctors and patients refer to red blood cells as cells, when in fact they are not. However, it does not make sense to change anything in the minds of citizens. Hearing that a child has anisocytosis, any parent will begin to show concern, since this term is most often simply not familiar to people who are not related to medicine. It should be noted that anisocytosis can be detected in both children and adults. Adolescence and childhood are characterized by anisocytosis with a predominance of microcytes, which is a sign of developing iron deficiency anemia. Otherwise, there are no differences between anisocytosis in an adult or in a child.
Erythrocytes are blood elements that have an oval shape, resembling a disk, convex on both sides. This allows the red blood cells to expand in size to carry out the function of gas exchange.
Normally, the diameter of erythrocytes is 7-8 microns, and their size is 5,5-9,5 microns (in graphical terms, this is the Price-Jones curve). The average volume of red blood cells (MCV) is 80-100 femtoliters. Such cells reflect normal indicators of human health, they are called normocytes and in the blood they should normally be more than the rest.
Devices that calculate the rate RDW, determine the amount of blood components such as:
MCH – average hemoglobin level (Hb).
MCHC is the average content of hemoglobin in each erythrocyte.
MCV is the mean volume of erythrocytes.
So, the normal RDW ranges from 11,5-14,5%. Anisocytosis can develop as a result of a lack of vitamin B12, iron and folic acid in the body, against the background of tumor diseases, after a blood transfusion, in violation of the hematopoietic function of the bone marrow, in chronic infectious diseases, in coronary heart disease.
When does anisocytosis develop?
Depending on the cause that caused anisocytosis, the sizes of red blood cells will vary, this applies not only to their diameter, but also to volume. In addition to normocytes, red blood cells of different sizes are found in the blood.
The heterogeneity of erythrocytes is said in the following cases:
Erythrocytes are greatly enlarged in size, swollen up to 9,5 microns or more. Such cells are called megablasts.
Somewhat smaller than megablasts will be blood cells called macrocytes.
If the red blood cells are small, they are called microcytes.
To determine the cellular composition of the blood, all analyzer devices use the following formula to calculate anisocytosis:
RDW(%) = SD/MCV(фл) * 100%
SD is the standard deviation of the volume Er, MCV is the average volume Er.
Anisocytosis may be high, but it is never low. If the values are below the norm, then this indicates a malfunction in the operation of the device, which is used to calculate the formula.
The need for a smear test
Although analyzer devices have become firmly established in diagnostic practice, this does not mean that laboratory assistants have been left without work. By placing a blood sample in the apparatus, the specialist simultaneously paints and dries a smear, which he will examine on his own.
If the entire field under study is filled with erythrocytes of the same size, then this is not displayed in the hemogram. If there are many abnormal red blood cells, then the doctor makes a note about anisocytosis. When large cells predominate in the blood, the doctor indicates macrocytosis, and when small blood cells predominate in the blood, then microcytosis.
It is also possible to detect mixed anisocytosis. In this case, half of the field will be occupied by anomalous cells, but it is simply impossible to determine which of them are more. In this case, it can be suspected that the patient has a deficiency of vitamin B12, folic acid, or pernicious anemia. In this case, the patient needs to undergo a detailed examination. Iron deficiency anemia is indicated by a smear pattern in which microscopic erythrocytes predominate.
It is worth noting that the analyzer cannot always determine the number of large and small red blood cells, which sometimes forces the laboratory assistant to perform manual calculations using the Price-Jones curve.
There are also several degrees of anisocytosis:
The number of altered cells is not more than 25% – slight anisocytosis. There will be one + in the results.
The number of altered cells does not exceed 50% – moderate anisocytosis. There will be two ++ in the results.
The number of altered cells does not exceed 75% – pronounced anisocytosis. The results will be three +++.
The number of altered cells is 100% – acute anisocytosis. There will be four ++++ in the results.
The Price-Jones curve displays the magnitude of the distribution of altered erythrocytes in diameter, and the histogram displayed by the analyzer device displays their distribution in volume.
Anemias and anisocytosis
Anisocytosis is a blood indicator that allows you to diagnose the following disorders:
If large erythrocytes predominate in the blood, then this may indicate a deficiency in the body of vitamin B12, folic acid and other hematopoietic factors that are involved in the processes of hematopoiesis. In this case, the doctor points to megaloblastic or macrocytic anemia.
If there are more microcytes in the blood, then this may indicate iron deficiency anemia. In this case, the doctor can diagnose microcytic anemia.
A normal number of red blood cells in the blood does not always mean that everything is in order with health. At the same time, aplastic anemia, which develops against the background of chronic diseases of the body, cannot be excluded.
If the erythrocytes in the blood are homogeneous, but changed towards macrocytes, then the MCV indicator should be taken into account. This allows you to make a differential diagnosis between different types of anemia.
Also, in order for the analysis to be as reliable as possible, it is necessary to compare the digital values uXNUMXbuXNUMXbissued by the analyzer with the histogram data, which display the number of red blood cells of different sizes.
Platelet anisocytosis
Modern devices allow you to count not only the number of erythrocytes, leukocytes, hemoglobin, erythrocyte index and leukocyte formula, but also the number of platelets, as well as platelet index and platelet anisocytosis (PDW).
For this purpose, the analyzers are equipped with electronic discriminators, which make it possible to differentiate:
macroplatelets.
Microerythrocytes.
Schizocytes (fragments of red blood cells).
Cellular debris (fragments of leukocytes).
PDW is an indicator of platelet anisocytosis, which should normally be 14-20%. These data are not essential in the diagnosis of diseases. The platelet distribution histogram is much more informative in this regard.
If anisocytosis increases, then myeloproliferative processes in the body can be suspected, and if it decreases, then leukemia, DIC, aplastic anemia, severe liver disease, and more.