Red blood cell distribution index (RDW) is a very important factor during a complete blood count. This indicator shows the size and shape of red blood cells.
Red blood cells perform the transport function, thereby assisting in the penetration of oxygen into all tissues and organs and at the same time taking away toxins and carbon dioxide accumulated in the cells. In their normal state, red blood cells are approximately the same size, which allows them to quickly stick together, forming blood clots.
The indicator of red blood cells in the blood may reflect the presence of pathological processes in the body, especially if the sizes of these cells vary significantly. Next, we will talk about in what situations the erythrocyte distribution index decreases, how this manifests itself and what it indicates.
Reduced RDW: norm and pathology
A person in good health has red blood cells of the same shape, density and color. In case of deviation, especially in the presence of autoimmune diseases or oncology, the failure occurs at the level of microcells, when young cells do not receive a certain number of components, which, in fact, inhibits their performance. Thus, anemia occurs - a pathology during which the body does not receive the required amount of oxygen, in other words, the metabolic function in red blood cells is disrupted.
What does RDW mean in a blood test?
During a general blood test, the erythrocyte distribution index is determined. If the presence of a specific disease is suspected, a blood test is prescribed to determine only this indicator.
Most often, the width of the distribution of red blood cells by volume is determined together with the MCV indicator. This is the average volume of red blood cells. This happens because these indices (in quantity and volume) are closely related to each other and help in determining the type of anemia.
It happens that the erythrocyte distribution index is reduced. What does it mean? The thing is that for a qualitative judgment about the state of red blood cells, not only their concentration in the blood is important, but also their shape. An increased distribution of red blood cells is observed in 1 out of 10,000 cases, but if the RDW index is reduced, which is much less common, we are talking about the presence of serious problems in the human body.
A blood test to determine the erythrocyte distribution index can be carried out both during medical examinations (routinely) and as prescribed, if there are suspicions of any abnormalities in the hematopoietic function. The analysis is required before surgery, during pregnancy and in childhood.
Leukocyte formula
NEU - neutrophils
The largest pool of leukocytes, accounting for 50 to 75% of the entire leukocyte population. This is the main link of cellular immunity. Neutrophils themselves are divided into band-nuclear (young forms) and segmented (mature). An increase in the level of neutrophils due to young forms is called a shift in the leukocyte formula to the left and is characteristic of an acute bacterial infection. A decrease may be a sign of a viral infection, and a significant decrease may be a sign of blood disease.
LYM - lymphocytes
The second pool of leukocytes after neutrophils. It is generally accepted that during an acute bacterial infection the number of lymphocytes decreases, and during a viral infection and after it it increases.
A significant decrease in lymphocytes can be observed with HIV infection, leukemia, and immunodeficiency. But this happens extremely rarely and is usually accompanied by severe symptoms.
EOS - eosinophils
Rare representatives of leukocytes. An increase in their number occurs during allergic reactions, including drug allergies, and is also a characteristic sign of helminthic infestation.
BAS - basophils
The smallest population of leukocytes. Their increase may indicate allergies, parasitic diseases, chronic infections, inflammatory and oncological diseases. Sometimes a temporary increase in basophils cannot be explained.
MON - monocytes
The largest representatives of leukocytes. These are macrophages that eat bacteria. An increase in values most often indicates the presence of an infection - bacterial, viral, fungal, protozoal. And also about the recovery period after them and about specific infections - syphilis, tuberculosis. In addition, it may be a sign of systemic diseases - rheumatoid arthritis and others.
Why is it necessary to do an RDW analysis?
It was already mentioned above that the index of distribution of red blood cells in the blood makes it possible to conduct a qualitative assessment of the composition of red blood cells, taking into account their size.
But why is this necessary? The thing is that these cells are very similar to each other, which gives them the opportunity to replace each other or form blastulas. An increase in cell size entails an increased need for nutrition and, in addition, this means that their life expectancy is reduced. All this directly affects the overall indicator of red blood cells in the blood and the human condition.
When a large number of red blood cells die, iron is released and more bilirubin becomes available, which puts increased stress on the liver, and as a result, it cannot process these substances.
The RDW index is directly related to the pathological process, during which the dimensions of erythrocytes change (anisocytosis). This condition is a complex chemical process that causes all blood cells to suffer.
Determination of the distribution width of red blood cells
The RDW value shows the heterogeneity (diversity) of red blood cells (Er) in size. Normally, the average erythrocyte volume (MCV) in an adult is from 80 fL to 95-100 fL (μm3). The appearance of small erythrocytes (microcytes) and/or large Er (macrocytes) is noted in blood pathologies.
Various types of anemia and myeloproliferative diseases are accompanied by changes in the size of red blood cells. Transformed Er appears in the blood, the sizes of which are smaller or larger than normal.
The range of Er size values from the smallest microcytes to the largest macrocytes is called the width of the erythrocyte volume distribution.
The following erythrocyte indices have clinical significance and are necessary for diagnosing anemia and bone marrow pathologies:
- RDW-CV is the coefficient of variation (CV) of Er dimensions;
- RDW-SD - means the relative width of the distribution of red blood cells by volume.
What the RDW-CV shows
The RDW-CV index is measured as a percentage and is calculated based on the Er distribution width graph. The coefficient of variation is calculated in the following way:
RDW-CV = SD*100%/MCV.
The calculated distribution of the width of CV erythrocytes depends on the average size of erythrocytes; if RDW- CV is increased, this may mean an increase in the number of macrocytes and an increase in microcytes.
The SD value is the deviation of the Er value from the average value to the greater and lesser sides from the midline on the graph.
Changes in this index can be monitored using the erythrocyte histogram.
- As the coefficient of variation increases, the shift of the histogram to the right increases when a significant number of macrocytes appear.
- The predominant content of microcytes leads to a shift of the histogram to the left, towards smaller values of erythrocyte cells.
RDW-SD index
The hematology analyzer calculates the RDW-SD indicator automatically and produces a ready-made result based on the red blood cell histogram. This blood index is measured in fl (µm3), and means the difference between the largest and smallest Er.
And if RDW- CV using a formula, then to calculate RDW- SD a red blood cell ( RBC) histogram is needed. On it, along the OX axis the Er values, measured in fl, are indicated, on the OY axis - the total number of erythrocytes in percent.
The RDW-SD value is numerically equal to the length of the straight line segment on the OX axis drawn on the erythrocyte histogram at the 20% level along the OY axis.
How is it calculated?
The RDW indicator is calculated as a percentage, the norm of which is considered to be the limit from 11.5 to 14.8. The red blood cell distribution index is determined using a mathematical equation that represents the ratio of modified red blood cells to their total mass.
Nowadays, laboratories use computer technologies that make it possible to calculate the percentage of deviation from the established norm. The calculation results are presented in the form of a histogram depicting a curve that indicates probable changes in the dimensions of red blood cells.
Normal indicators
The norms of the erythrocyte distribution index depend on gender, age and the presence of certain conditions that occur in the human body. For children under one year of age, the normal rate is 11.5-18.7%. At one year of age and older, the values tend to the generally accepted norm of 11.5-14.5%.
For the female half of humanity, the upper limit shifts to 15.5%, since their hormonal levels change too often: during pregnancy, lactation, taking oral contraceptives, menopause.
For analysis, blood is taken on an empty stomach in the morning (before 9 am). It is very important that before this procedure the person does not take any medications and is in a balanced internal state.
Raising RDW
The RDW level can be elevated in some situations. The most common cause of this pathology is iron deficiency anemia. The indicator can change at different stages of pathology development, which is clearly reflected in the histogram of red blood cells:
- The initial stage of anemia development is characterized by normal indices, but hemoglobin will be greatly reduced. This is the result of healthy functioning of the spinal cord.
- The next stage of development in the histogram will show an increase in RDW. When there are problems with hemoglobin, indicators such as the average concentration and content of hemoglobin in a blood cell and the average volume of red cells decrease.
When treating IDA, it is necessary to normalize the level of concentration of iron-containing protein and its characteristics in the human blood.
Pathological consequences
Normal RDW
Anemia with normal RDW may indicate thalassemia. A low Mentzer index, calculated from a complete blood count, may indicate this disease, but hemoglobin electrophoresis may be diagnostic. Anemias of chronic diseases show normal RDW.
High RDW
High RDW may result from the presence of fragments, agglutination groups, and/or abnormally shaped red blood cells.
- Iron deficiency anemia usually presents with a high RDW and low MCV.
- Anemia caused by folic acid and vitamin B 12 deficiency usually manifests as a high RDW and a high MCV.
- Anemia with mixed deficiency (iron + B 12 or folic acid) usually presents with a high RDW and variable MCV.
- Recent bleeding is usually accompanied by a high RDW and normal MCV.
- If instead
citrated bloodused
blood with anticoagulant
EDTA, a falsely high RDW value may occur. Cm.
Pseudothrombocytopenia
What do the reduced numbers mean?
Patients often ask what this means: “red blood cell distribution index is reduced.” Since the erythrocyte distribution index cannot be assessed without a volume indicator, it is necessary to familiarize yourself with all the options for underestimated indicators and their relationship:
- RDW is low and MCV is below average - indicating problems with the spleen and liver.
- RDW is lowered, and MCV is higher than the normal level - indicates the presence of oncological pathologies, mainly the development of metastases in the bone marrow.
The fact that the erythrocyte distribution index RDW sd is reduced, from a biological point of view, cannot, in principle, be observed. For this reason, most often the patient is offered to donate blood again, observing the following conditions:
- stop smoking and drinking alcohol for 24 hours before blood sampling;
- do not take any medications before the analysis;
- Avoid eating smoked and salty foods the day before.
In the case when the erythrocyte distribution index RDW sd is indeed reduced, which is necessarily confirmed by deviations from the norm in the MCV indicator, then this indicates the occurrence of certain pathologies. These include:
- Hypochromic microcytic anemia - sometimes also called anemia. A condition in which irregularly shaped red blood cells die because they have no biological value in the body.
- Malignant tumors - usually in this case we are talking about mastopathy, bone marrow and lung cancer.
- Hemolysis of red blood cells is a process during which red blood cells die without reaching their target. As a result, active hemoglobin is released.
What do abnormalities in women indicate?
The hemogram analysis may reflect an increased level of immune cells if women have one of these diseases:
- viral hepatitis A;
- acute infectious disease of the respiratory tract;
- viral disease with a high level of susceptibility (measles);
- a viral disease manifested in a rash (rubella);
- a bacterial infection that results in coughing fits.
The normal number of immune cells may be shifted upward if a woman suffers from an endocrine disease, hypothyroidism or thyrotoxicosis.
The level of lymphocytosis can be increased in cases of cancer and metabolic disorders in the body.
Decoding the quantitative indicator of immune cells will be completely different if few of them are identified.
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In this case, women can be diagnosed with tuberculosis, which affects small areas of the respiratory system.
For this reason, toxic substances enter the blood, and the body is in a state of severe stress.
A decrease in the level of lymphocytes is associated with the appearance of cancer in a woman - multiple myeloma.
Together with a decrease in the number of immune cells, this serious illness can lead to the detection of a large amount of protein in urine.
But this disease proceeds in a special way: its initial stage is characterized by an increased level of immune cells, but later (as the tumor grows) there are very few lymphocytes.
The normal content of immune cells is often disrupted due to the occurrence of radiation sickness.
Since the maturation process of blood cells is disorganized, the body stops fighting germs and viruses. This disease can occur in an acute form if the exposure was strong and one-time.
The disease becomes chronic if irradiation is periodic, but its doses are small.
Decreased levels of immune cells may be caused by bone marrow dysfunction. At the same time, it loses the ability to produce the required volume of blood cells and becomes connective tissue.
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For this reason, the blood has a low amount of all formed elements. Also, immune cells die during HIV infection.
When the norm of lymphocyte content is violated, it is recommended to undergo a comprehensive examination. After additional tests, the doctor will know what kind of disease the patient has.
Based on the data obtained, the appropriate treatment will be selected.
Causes
So, the erythrocyte distribution index is reduced - what does this mean? There are several reasons that can reduce the RDW indicator:
- Acute blood loss due to injuries and pathological bleeding.
- Frequent operations.
- A metabolic disorder during which the food consumed is not completely digested.
- Hormonal imbalance, which most often occurs in women.
- Deficiency of B vitamins and iron in the body.
- Blood diseases characterized by rapid destructive processes.
What measures to take?
What to do when the red blood cell distribution index is low?
A highly qualified doctor during a consultation will most likely ask the patient to take the test again, because the RDW indicator is almost never underestimated. Because this suggests that all cells are ideal in their parameters, but this cannot happen in principle. If the indicator is confirmed by repeated analysis, then a full examination of the body’s condition is carried out, paying special attention to oncological examinations.
It's important to understand
Sometimes a person informed by a doctor about a decrease in the distribution of red blood cells by volume becomes very frightened. You should not immediately get upset and panic, since the test result does not always indicate the presence of a difficult-to-treat disease.
Having received the test result, a person should contact a highly qualified specialist. Only a good doctor will be able to correctly “decipher” the result, establish the cause and, if necessary, prescribe appropriate therapy.
Preventive measures
You can prevent a reduced RDW by following these simple rules:
- The diet should be balanced, which includes plenty of fresh fruits, lean meats and vegetables.
- It is recommended to breathe fresh air as often as possible.
- An active lifestyle will help prevent a decrease in the RDW index.
- It is very important not to skip routine medical examinations, during which most often serious deviations from the norm are detected that do not have external symptoms.
As a result, we learned that the red blood cell distribution index reflects their dimensions relative to each other and makes it possible to learn about their biological value. A decrease in RDW is very rare, but if the erythrocyte distribution index is decreased, this means that various pathologies may be present.
The index is calculated based on the results of a general blood test, but can only be fully valid in conjunction with the MCV indicator, since they are closely interrelated.
What do the results depend on?
RDW CV and SD values in the absence of health problems should correspond to established standards, which differ depending on the patient’s age and gender.
Any deviations up or down are a sign that pathological processes are occurring in the body or diseases are developing. But it also happens that the examination result turns out to be false positive. The causes of a laboratory error are a person’s failure to follow recommendations regarding proper preparation for blood sampling or incorrect actions of medical personnel.
If the result shows deviations from the norm, the analysis must be repeated to ensure the reliability of the results and eliminate errors.
