Anisocytosis In A General Blood Test - What Is It? Norm, How To Pass?

2024 Author: Josephine Shorter | [email protected]. Last modified: 2024-01-07 17:49

Anisocytosis: what is it, what is the norm?

Anisocytosis of erythrocytes (red blood cells) is an indicator that reflects the width of their distribution. This measure is indicated in the analysis results as RDW. Previously, the Price-Jones curve was used to determine anisocytosis, which was rather 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, subject to the correct operation of the instruments. Therefore, the determination of anisocytosis in modern medicine is a task that falls on the analyzing device, and not on the laboratory assistant.

Content:

• The rate of erythrocytes in the blood
• When does anisocytosis develop?
• The need to pass a smear
• Anemia and anisocytosis
• Platelet anisocytosis

The rate of erythrocytes in the blood

Historically, both doctors and patients refer to erythrocytes as cells, although in reality they are not. However, it makes no 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 not familiar to people who are not related to medicine. It should be noted that anisocytosis can be detected in both children and adults. For adolescence and childhood, anisocytosis with a predominance of microcytes is characteristic, 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, reminiscent of a disc, convex on both sides. This allows erythrocytes to grow in size for the function of gas exchange.

Normally, the diameter of erythrocytes is 7-8 microns, and the physiological norm is their size of 5.5-9.5 microns (in graphical terms, this is the Price-Jones curve). The average red blood cell volume (MCV) is 80-100 femtoliters. Such cells display normal indicators of human health, they are called normocytes and in their blood, normally, there should be more than others.

Devices that calculate the RDW rate determine the amount of such blood components as:

• MCH is the average hemoglobin (Hb) level.
• MCHC is the average hemoglobin content in each erythrocyte.
• MCV is the average volume of erythrocytes.

So, the normal RDW is in the 11.5-14.5% range. 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 ischemic heart disease.

When does anisocytosis develop?

Depending on the cause that caused the anisocytosis, the size of erythrocytes will differ, this applies not only to their diameter, but also to their 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 increased in size, swollen to 9.5 microns or more. These cells are called megablasts.
• Somewhat smaller than megablasts are blood cells called macrocytes.
• If the red blood cells are small, they are called microcytes.

To determine the cellular composition of blood, all analyzers use the following formula to calculate anisocytosis:

RDW (%) = SD / MCV (fl) * 100%

SD is the standard deviation of the Er volume, MCV is the average Er volume.

Anisocytosis can be high, but it is never low. If the values are below the norm, then this indicates a malfunction in the device, which is used to calculate the formula.

The need to pass a smear

Although analyzer instruments have become firmly established in diagnostic practice, this does not mean that laboratory technicians are out of work. By placing a blood sample in the apparatus, the specialist simultaneously paints and dries the smear, which he will examine independently.

If the entire investigated field 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 of 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 abnormal cells, but it is simply impossible to establish which of them are no longer possible. In this case, it can be suspected that the patient is deficient in 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 prevail.

It is worth noting that the analyzer is not always able to determine the number of large and small red blood cells, which sometimes forces the laboratory assistant to perform calculations manually, using the Price-Jones curve.

There are also several degrees of anisocytosis:

• The number of changed cells is not more than 25% - a slight anisocytosis. There will be one + in the results.
• The number of changed cells does not exceed 50% - moderate anisocytosis. There will be two ++ in the results.
• The number of changed cells does not exceed 75% - pronounced anisocytosis. The results will contain three +++.
• The number of changed cells is 100% - acute anisocytosis. The results will be four ++++.

The Price-Jones curve displays the magnitude of the distribution of the altered erythrocytes along the diameter, and the histogram displayed by the analyzer displays their distribution along the volume.

Anemia and anisocytosis

Anisocytosis is a blood indicator that can be used to diagnose the following disorders:

• If large erythrocytes predominate in the blood, 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 indicates 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.
• The normal number of red blood cells in the blood does not always mean that everything is in order with health. At the same time, it is impossible to exclude aplastic anemia, which develops against the background of chronic diseases of the body.

If 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, for the analysis to be as reliable as possible, you need to compare the digital values produced by the analyzer with the histogram data, which display the number of red blood cells of different sizes.

Platelet anisocytosis

Modern devices allow 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.
• Micro-erythrocytes.
• Schizocytes (fragments of red blood cells).
• Cellular debris (leukocyte fragments).

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 in this regard is much more informative.

If anisocytosis increases, then myeloproliferative processes in the body can be suspected, and if it decreases, then leukemia, disseminated intravascular coagulation syndrome, aplastic anemia, severe liver disease and more.

The author of the article: Shutov Maxim Evgenievich | Hematologist

Education: In 2013 he graduated from the Kursk State Medical University and received a diploma "General Medicine". After 2 years, completed residency in the specialty "Oncology". In 2016 completed postgraduate studies at the National Medical and Surgical Center named after N. I. Pirogov.