What is the RDW indicator in a general blood test? The width of the distribution of red blood cells by volume is higher than normal

RDW in a blood test is a measure of the degree of anisocytosis, or the heterogeneity of red blood cells in volume. This test determines the presence of red cells in the blood that are significantly larger in volume than the average value, and the difference between large and small cells. The meaning of this abbreviation is “distribution of red blood cells by size.”

What is RDW?

Erythrocytes are red, biconcave, disc-shaped bodies that color the blood accordingly. They form the basis of blood and supply oxygen to tissues and organs. In healthy people they do not differ in volume, color and shape. The proper functioning of red blood cells does not depend on their diameter, but rather on their volume. Its average is designated MCV. In healthy people, this value may vary within small limits. In medicine, this range is called erythrocyte heterogeneity, or volume distribution width. Typically, red cells decrease in volume as a person ages, so there is a difference between them. In addition, it may be associated with anemia or malignant tumors. The appearance of red blood cells of different volumes in the blood is called anisocytosis. In order to determine changes, the doctor orders a blood test for RDW.

In what cases is the analysis carried out?

Blood for RDW is tested when the patient undergoes a general test, which is prescribed routinely or for diagnosing various pathologies, as well as before surgical interventions. They may offer to donate blood for this indicator if there is a suspicion of anemia.

This examination is mainly intended for differential diagnosis of different types of anemia, as well as for monitoring their treatment.

How is the research going?

Modern analyzers allow you to quickly and with high quality carry out blood tests, assess the condition of red blood cells during treatment, and decide on further therapy. They count the number of red blood cells of different sizes per 1 μl of blood. Analyzers calculate the average volume of the red cell and determine the degree of deviation from the normal value of this parameter. The result is displayed in the form of a histogram.

The test may give a false positive result. This is due to the fact that the blood contains many modified red blood cells called macrocytes. For greater reliability, the Price-Jones curve is examined.

The most accurate analysis result for RDW SD (standard deviation) and RDW CV (coefficient of variation) is obtained by manual calculation, but this method is very labor-intensive and time-consuming, so it is practically not used at present.

Blood for RDW is taken from a vein in the elbow

If all indicators are normal, the result is negative. If the RDW is elevated, the result is considered positive. Typically, in this case, a re-examination is required to determine the exact cause of the increase, since after one blood draw the diagnosis cannot be considered final. The fact is that RDW can be elevated immediately after a blood transfusion or surgery. In any case, if a positive result is obtained, a repeat blood donation is required, followed by a histogram examination. The distribution and modification of red blood cells can change quickly and frequently.

How is the procedure performed?

Blood is drawn on an empty stomach from a vein in the elbow area. In infants and young children it is usually taken from the finger.

Analysis transcript

The RDW norm is 11.5-14.5% for adults, regardless of age, 14.9-18.7% for children under six months, 11.6-14.8% for children over six months. If the value is less than or exceeds the norm, it is necessary to be examined for diseases and undergo treatment.

In children and adults, RDW is increased with anemia (iron deficiency, hemolytic, megaloblastic), vitamin B12 and folate deficiency, and liver diseases.

An RDW level below normal levels may indicate the development of various types of anemia.

When interpreting the analysis, MCV values are taken into account. This helps in diagnosis to distinguish between different types of microcytic anemias. If RDW is normal and MCV is low, this may indicate diseases such as:

blood transfusion;
thalassemia;
hemorrhage;
post-traumatic splenectomy;
malignant tumors and a course of chemotherapy.

If, with a decreased MCV, the RDW indicator is increased, this may indicate beta thalassemia, iron deficiency, and erythrocyte fragmentation. With increased MCV and normal RDW, we can talk about liver disease.

If both indicators are high, then there is a possibility of vitamin B12 deficiency, hemolytic anemia, and cold agglutination. In addition, this result is observed during chemotherapy.

Video about the method of collecting blood from a vein for RDW research:

Finally

Analysis for RDW is of great importance in medicine, especially in the differential diagnosis of various types of anemia.

There are certain types of diseases that are detected in the early stages using an RDW blood test. Because the presence of various pathologies (or absence thereof) is influenced not only by the number and volume of red blood cells, but also by the presence of red cells in the blood, whose volume significantly exceeds the average.

What it is

Red blood cells are the basis of blood. They are red cells. They are the ones that color the blood red. Red blood cells provide oxygen to all human tissues and organs. A healthy person’s blood contains red blood cells that are the same in size, shape and color.

Their correct operation is greatly influenced by the volume of red blood cells, but not the diameter. The average volume of red blood cells is characterized by the MCV parameter. In a healthy person, this indicator is within small limits. Such fluctuations (that is, the range from the smallest erythrocyte volume to the largest) in medical terminology are usually called the width of the erythrocyte distribution or the heterogeneity of erythrocytes. The diagnostic that establishes this characteristic is called RDW.

As you know, in the blood of a healthy person there are red cells of various sizes. Medical experts call this phenomenon anisocytosis. Its parameter is the main indicator (index) of blood cells. This index is usually denoted RDW - this is an abbreviation for the English name red cell distribution width. The RDW parameter is calculated based on the standard deviation of the red blood cell volume from the MCV. Anisocytosis is also detected when examining a blood smear, but obtaining results takes longer than when identifying RDW in a blood test. Basically, such a blood test is carried out on hematological equipment, while modern technologies make it possible to diagnose a blood sample using several parameters simultaneously. A modern analyzer establishes the average volume of red blood cells, as well as the degree of deviation from the norm of this parameter.

General blood test and decoding of RDW indicator

The RDW indicator is studied during general (clinical) blood diagnostics. Such an analysis can be prescribed both routinely and to identify many types of diseases. Patients also undergo a general blood test before surgery. And a repeated clinical blood test can be prescribed for those people who are undergoing therapy for anemia.

When analyzing blood, the RDW indicator is used in conjunction with the MCV indicator. This combination helps to determine, during a differentiated assessment of characteristics, one or another type of microcytic anemia. With a low MCV, a normal RDW may be observed, which is an important indication of symptoms of diseases such as thalassemia, blood transfusion, hemorrhage, post-traumatic splenectomy. In addition, such RDW indices can occur in malignant neoplasms and chemotherapy. If, with the same low MCV, an increased RDW is observed, this may indicate the presence of iron deficiency, beta thalassemia or red blood cell fragmentation.

A situation may also occur when the MCV characteristic is overestimated, and the RDW blood parameter is normal. This combination indicates liver disease. And with elevated MCV and RDW parameters, a blood test indicates the presence of diseases such as B12 deficiency anemia, cold agglutination and hemolytic anemia. In addition, these characteristics of red blood cells are also encountered during chemotherapy.

Heterogeneity of erythrocyte parameters is normal

The use of hematological analyzers in modern medicine contributes to the rapid and high-quality study of the entire human circulatory system. They help to assess the state of red cells in a person’s blood during the treatment period, as well as establish directions for further therapy. But all analyzers are based on the blood test method.

Heterogeneity of erythrocytes is the appearance in the blood of red cells of different volumes. But their predominant number indicates certain diseases. It is generally accepted that the RDW rate in the blood should not exceed 11.5-14.5%.

When characterizing the erythrocyte RDW index, it should be taken into account that this parameter does not depend on the average size of the erythrocyte. Therefore, in some cases, deviations from the norm RDW in the blood may not appear. This is due to the fact that a large number of red blood cells of an already modified type are present in the blood. They are often called macrocytes. And their appearance in the blood gives false positive results during diagnosis. Reliable data in such cases can be obtained by studying the Price-Jones curve.

During differentiated diagnosis of anemia, the RDW norm in a blood test is determined by the MCV indicator, the characteristics of which must also be normal (that is, the MCV indicator is normal, RDW is also normal).

Increasing the indicator

The RDW indicator is elevated in the blood test in several cases. First of all, an increase in this indicator is the main sign of iron deficiency anemia. But elevated characteristics may also indicate chronic liver disease, folate or vitamin B12 deficiency.

Iron-deficiency anemia is the most common type of anemia. And at different stages of disease development, the RDW indicator is increased unequally. This is clearly visible on the erythrocyte histogram. It is known that in the initial stage of iron deficiency anemia, red blood cells are within normal limits, but the amount of hemoglobin will be at the lower limit of normal (or reduced). Such characteristics indicate normal activity of human bone marrow.

In the second stage of iron deficiency anemia, the red blood cell histogram begins to expand to the left (that is, increase), and the RDW increases. Disturbances in hemoglobin formation cause a decrease in parameters such as MCV (average erythrocyte volume), MCH (average hemoglobin content in an erythrocyte), MCHC (average hemoglobin concentration in an erythrocyte), but anisocytosis of erythrocytes will always be increased. And such changes are clearly visible on the histogram. It will noticeably increase to the left. When treating anemia of this type, the level of hemoglobin content and its main characteristics in the blood is normalized. This is achieved by taking iron supplements.

I continue to introduce you to the decoding of abbreviations that can be seen in the analysis form that is issued by the hemolytic analyzer. In this post we will talk about such an indicator as RDW in a blood test,or the width of the distribution of red blood cells, which is determined by most modern instruments. This is one of the erythrocyte indices, among which should also be mentioned , .

The RDW index reflects the heterogeneity of red blood cells, is a measure of the dissimilarity of the red blood cell population by volume, and indicates variations in red blood cell volume. The coefficient is used as an auxiliary criterion for diagnosing anemia.

RDW SD and RDW CV: decoding, norm, differences

With the decoding of RDW in the blood test, the situation has become a little clearer, but this is only the tip of the iceberg. There are two RDW measures. These are RDW-CV and RDW-SD - they both determine the variability of red blood cells in size.

The first index is deciphered as the relative width of the distribution of red blood cells by volume (coefficient of variation). RDW-CV in a blood test is influenced by MCV, with fluctuations in which there will be a tendency to increase the described indicator. To make it clearer, look at the calculation formula:

RDW-CV= SD/MCV 100

Here SD acts as the standard mean square deviation of the red blood cell volume from the average number. The RDW-CV index indicates how much red cell volume differs from the average. It is measured as a percentage, normally it amounts to 11,5%-14,5% , which indicates the existence of a homogeneous population of cells (normo-, micro- or macrocytes).

The erythrocyte coefficient RDW-SD in a blood test is deciphered as the relative width of the distribution of erythrocytes by volume (standard deviation). It shows how different these cells are in size and volume, that is, what the difference is between a tiny red blood cell and a very large one. This calculated indicator is not subject to MCV; it is measured in femtoliters (fl). His norm is 42±5 fl.

If we consider the differences in these two versions of RDW, then it should be said that RDW-SD is considered a more accurate index in the presence of a small population of macrocytes (red blood cells with a diameter greater than 7.9 microns) or microcytes (diameter

RDW in blood test is increased

An increase in RDW by more than 15% indicates the presence of cells of heterogeneous volume (micro-, normo-, macro- and schizocytes). The higher the score, the greater the discrepancy in the size of red cells. This phenomenon is called anisocytosis. The width of the distribution of red blood cells above normal can be the result of many reasons, which include:

microcytic anemia;
blood transfusions;
Iron-deficiency anemia;
oncopathologies with metastases to the bone marrow;
folic acid deficiency;
alcoholism;
myelodysplastic syndrome.

An increased width of distribution of erythrocytes is also observed in chronic liver damage (against the background of normal MCV), lead poisoning, Alzheimer's disease, microspherocytosis, hemoglobinopathies, bone marrow metaplasia, as well as in cardiovascular diseases.

RDW in blood test is reduced

If in the analysis the width of the distribution of red blood cells is below normal, then this fact indicates the need to retake the tests. Because the analyzer shows either an overestimated value or a normal value. In principle, the width of the distribution of red blood cells cannot be reduced, and such a result is not diagnostically valuable.

March 6, 2017 | Elena Kolchina |

No comments yet

The erythrocyte distribution index is decreased or increased: what does this mean?

Red blood cell anisocytosis (RDW) is an index of red blood cell distribution based on magnitude. This parameter evaluates in a blood test the number of red blood cells of various sizes that deviate from the normal value. It is a percentage visualization of red blood cell heterogeneity.

What indicator is considered normal?

In an adult, this figure is normally in the range of 11.5-14.5%.

Microcytes are considered to be red blood cells smaller than 6.7 microns. Macrocytes are larger than 8 microns in size. The study of this indicator is informative in determining the type of anemia. Microcytosis in the analysis indicates the presence of iron deficiency anemia, the development of microspherocytosis, thalassemia, sideroblastic anemia. Macrocytosis is characteristic of deficiency anemia (lack of folic acid) and toxic liver damage. A general increase in anisocytosis is observed in macrocytic anemia, iron deficiency anemia, bone marrow lesions, myelodysplastic syndrome, and hemolytic anemia.

In newborns, physiological macrocytosis is observed, which lasts up to two months of life. In parallel with the anisocytosis index, it is necessary to study the MCV, which takes into account the size of red blood cells, their average volume, and the hemoglobin content in them.

General rules for preparing for blood tests

For three days it is recommended to exclude: alcoholic drinks, smoked foods, fried and fatty foods. A few hours before the test, it is not advisable to smoke or exercise. If possible, you should stop taking medications a week before blood sampling (with the exception of monitoring therapy). Tests are not performed after physiotherapeutic procedures, massage, ultrasound diagnostics, rectal examination and radiography.

Increase and decrease in erythrocyte anisocytosis

Iron deficiency anemia is considered the most common cause of changes in the erythrocyte distribution index.

This is a disease that occurs as a result of iron deficiency and is accompanied by impaired heme synthesis, leading to anemia of varying severity.

This blood pathology is quite common and accounts for about 80% of all anemias. Most often, it occurs in women, children and adolescents.

Classification

Juvenile - caused by a violation of iron metabolism due to hormonal imbalance, intensive growth and the formation of the menstrual cycle in girls.
The acute posthemorrhagic form is associated with the loss of a large amount of blood in a short period of time.
Chronic posthemorrhagic iron deficiency anemia occurs with prolonged blood loss (heavy menstruation, hemorrhoids, frequent nosebleeds, untreated gastric ulcer, Crohn's disease, ulcerative colitis, diverticulitis).

According to the degree of severity, they are divided into mild (Hb within 100-110 g/l), moderate (Hb not less than 80 g/l), severe (Hb below 75 g/l). The risk group for the occurrence of iron deficiency anemia includes: women who breastfeed for more than a year, carrying a fourth or more child, patients with chronic blood loss, donors, vegetarians.

The development of this disease occurs in several stages. Initially, prelatent and latent iron deficiency is observed, accompanied by its depletion in organs and tissues. Clinical symptoms appear at the stage of reduction of iron in heme-containing pigments, necessary for the synthesis of hemoglobin.

Clinical picture

The manifestation is a nonspecific anemic syndrome, manifested by pallor of the skin and mucous membranes, drowsiness, weakness, and decreased performance.

Next comes dystrophic lesions of the nails (delamination of their structure, spoon-shaped shape, slower growth). Patients complain of constant dry mouth, difficulty swallowing dry food, the appearance of perverted taste preferences (the desire to eat chalk, raw meat, soil), and a change in the sense of smell. The most characteristic manifestations are considered to be: the occurrence of jams in the corners of the mouth and smoothing of the relief of the tongue (disappearance of the papillae).

During an objective examination, attention is paid to a yellowish-gray tint of the face, dryness and flaking of the skin, and a bluish tint to the sclera.

Diagnostics

The basis for making a diagnosis is characteristic complaints and clinical symptoms, hypochromic microcytic anemia in the CBC.

The color index and hemoglobin saturation level of erythrocytes are also below normal. Severe anemia is characterized by pronounced anisocytosis (the erythrocyte distribution index shifts towards microcytosis) and the development of poikilocytosis. Bone marrow regenerative parameters are not impaired. There is no decrease in the number of reticulocytes.

Indicative are the ferritin level and transferrin saturation coefficient (reduced).

Assessment of specific parameters

Iron deficiency anemia is characterized by a decrease in the average diameter and volume of erythrocytes and an increase in the average RDW value.

A distinctive feature is a decrease in iron-containing red blood cells (siderocytes).

To carry out differential diagnostics with lead intoxication, basophilic punctuation of erythrocytes (in case of poisoning - rougher) and the level of free basophilic protoporphyrin (increased, more than 9.0 µmol/l in case of lead intoxication) are assessed.

Treatment of iron deficiency conditions

The priority is to eliminate background diseases accompanied by chronic blood loss, as well as normalize nutrition.

Simultaneously with the medicinal elimination of iron deficiency, a diet with an increased amount of dietary iron and vitamin C is prescribed, and the consumption of dairy products is limited.

As drug therapy, divalent forms (Totema, Vi-fer, Aktiferrin, Sorbifer) are most effective. The effectiveness of therapy and the increase in hemoglobin levels are assessed every week. In pregnant women, it is advisable to add folic acid to therapy (even if its levels are normal in a blood test).

It is important to remember that preventive measures to prevent iron deficiency in children must begin in the antenatal period. From the second trimester of pregnancy, all women must be prescribed a maintenance dosage of iron supplements. In the postnatal period, children receiving artificial feeding and born from multiple pregnancies are given preventive courses.

Folate deficiency anemia

Folate deficiency develops in the human body.

The disease most often occurs in children, young and middle-aged people, and pregnant women. Also, the risk group includes patients with celiac enteropathy, Crohn's disease and ulcerative colitis, and intestinal cancer.

Clinical picture

Patients complain of weakness, dyspepsia, aversion to food, pain and burning of the tongue, glossitis.

Objectively assessed: pallor of the skin and subicerial sclera, crimson tongue with a smoothed relief. During auscultation of the heart, arrhythmias, extrasystoles, and systolic murmur at the apex are detected.

Diagnostics

A clinical blood test revealed anemia, macrocytosis and an increase in the erythrocyte distribution index. Folic acid levels are below normal with generally normal iron and vitamin B12 levels.

Serum and erythrocyte folate levels are assessed.

Treatment

In the vast majority of patients, folic acid in a dosage of 1 to 5 mg is sufficient to treat folate deficiency anemia. For intestinal diseases, the dose is increased to 15 mg/day.

The minimum duration of prescribed therapy is one month. The treatment is monitored every two weeks.

The following hemogram indicators are assessed:

level of red blood cells and hemoglobin;
red blood cell distribution index;
increase in the number of reticulocytes.

In the presence of enteropathies, it is necessary to prescribe regular preventive courses of folic acid preparations.

Malignant bowel diseases

Accompanied by severe posthemorrhagic iron deficiency and folate deficiency anemia, with a pronounced increase in the erythrocyte distribution index.

Changes in these indicators in combination with clinical symptoms make it possible to identify the disease in the early stages and increase the patient’s chances of survival and further return to a full life.

The initial manifestations are nonspecific and are characteristic of all neoplasms: symptoms of general intoxication (weakness, chills, fever, muscle and joint pain, refusal to eat), progressive weight loss is observed. Then dyspeptic disorders (nausea, vomiting), bloating, flatulence, diarrhea are added, and if the rectum is damaged, a false urge to defecate appears. Sometimes patients pay attention to streaks of blood in the stool.

As the tumor grows, the general symptoms change to specific ones, characteristic of intestinal cancer. The amount of blood in the stool increases, and complete staining of the stool is possible. This leads to significant anemia in the patient. There is also frequent alternation of long-term (up to 10 days) constipation and diarrhea, pain during bowel movements, a constant feeling of incomplete evacuation, and possible sensation of a foreign body in the intestine. Characterized by a sharp, fetid odor of feces, a high content of mucus, the appearance of streaks of pus, and a putrid odor from the mouth. In women, a tumor may grow into the vagina, followed by the discharge of pus, mucus and feces.

Diagnostics

Further research includes:

Digital examination (informative for damage to the rectum).
Irrigoscopy (contrast, X-ray examination of the intestine) and colonoscopy (the gold standard examination for suspected oncological lesions of the intestine, allows you to identify the location and estimate the size of the tumor, and perform a targeted biopsy).
Fibercolonoscopy with tumor biopsy.
Sigmoidoscopy (visualizes the rectum and sigmoid colon);
Computed tomography, radiography, magnetic resonance imaging of organs, ultrasound, ECG, Echo-CG.
In women, a vaginal examination is required (possible overhang of the vaginal vault as a result of tumor pressure).
Fecal occult blood test.

A complete blood count for bowel cancer reveals anemia, a decrease in platelet count, leukocytosis and a sharply increased ESR (erythrocyte sedimentation rate).

Biochemical analysis will show significantly elevated levels of urea and creatinine. The haptohemoglobin level is sharply increased, the level of total protein, potassium and sodium ions is decreased.

Treatment prognosis

The choice of therapy and its effectiveness are directly dependent on the stage of the disease, the location of the tumor and the presence of metastases. Survival rate with timely treatment (stage 1) is up to 95%.

Basic treatment methods

The use of isolated chemotherapy and radiation treatments for colon cancer is not effective.

At stage 1, excision of the tumor is recommended, and, if necessary, resection of the area of the intestine affected by the tumor. Follow-up with an oncologist.
Stage 2 therapy consists of resection, followed by the formation of an anastomosis. Combination of radiation (chemotherapeutic) methods with surgery.
At stage 3, combined chemo-radiotherapy is required.
Stage 4 treatment is usually not effective. Palliative tumor resection is used in conjunction with combination therapy.

Prevention of intestinal cancer includes quitting smoking, normalizing nutrition (sufficient consumption of food rich in plant fiber, fresh fruits and vegetables), maintaining a healthy weight, active lifestyle, and regular preventive examinations.

At the same time, in normal RDW blood, the volume size of erythrocytes is 6.9-7.4 microns, and other sizes can be called pathologies:

< 6,9 мкм – микроциты (с латинского – маленькие клетки). В норме крови на них должно приходиться меньше 15% всех эритроцитов.
6,9 < объем эритроцита < 7,4 – нормоциты (нормальные клетки). В норме на них должно приходиться не менее 70% всех эритроцитов;
7,4 < объем эритроцита – макроциты (большие клетки). В норме на них должно приходиться меньше 15% всех эритроцитов

The normal RDW in a blood test for an adult is 11-14%.

Why is a test prescribed?

Usually, RDW is included in the list of mandatory tests during clinical examination, since it can identify the early stages of diseases, but in some cases the doctor may prescribe a blood donation specifically for this indicator separately.

Before surgery, it is very important for the doctor to find out the RDW value in the patient's blood test, because it can indicate the presence of anemia. And in some cases, the result of an RDW test may be a contraindication to surgery or medication used during the procedure.

Relegation and Promotion

Normally, in a blood test for RDW, the doctor will see more than 70% normocytic cells. Other indications can be considered deviations that appear as a result of various diseases. Usually the blood test for RDW is either high or low.

So, if a low RDW is detected in a blood test, one can judge whether a person has . At the same time, this indicator is important for diagnosis, so with a normal average volume of erythrocytes and a reduced RDW, one can judge the presence of microcytic anemia.

If the average red blood cell volume is reduced, and the RDW of the blood, on the contrary, is normal, then the patient is prone to hemorrhage (the scientific name for hemorrhages), (a genetic disorder that affects the synthesis of hemoglobin, which affects the synthesis of red blood cells) or the processes accompanying the complete removal of the spleen - the site death of red blood cells.

A patient with a decreased RDW will experience mild fatigue, lethargy and drowsiness, and sometimes rapid breathing and severe shortness of breath. The clinical picture will resemble anemia. This is because small red blood cells will deliver less oxygen to the tissues than normal-sized red blood cells. The nervous system will primarily “suffer” from this, which will manifest itself in the symptoms described above.

So, when using iron-containing drugs, red blood cells may slightly increase due to new iron, but this will appear in large numbers only a month and a half after the start of treatment. Therefore, it is important to take all prescribed tests on time, because thanks to this the doctor will be able to track the progress of treatment.

How to prepare

Preparing for a blood test for RDW is no different from preparing for a general blood test. The doctor recommends that the patient comply with the hospital regime, and if the treatment is carried out on an outpatient basis, then follow the following general recommendations:

, in the morning.
A week before the day of the RDW test, it is very important to give up alcoholic beverages.
During the same week, it is recommended to adhere to, that is, excluding fried, spicy, fatty and canned foods from the diet.
If possible, 3 days before the test, avoid medications that especially affect the level of iron in the blood. If cancellation is impossible, the attending physician informs the patient about this, and also indicates this on the form and the referral for tests.
In the morning, it is advisable to eat only light food without sugar. Coffee and strong black tea will also negatively affect the analysis results.
Do not smoke 3 hours before the test.
It is recommended to sit near the office and relax 15 minutes before the test.

All these recommendations are related to the fact that if this schedule is not followed, a sufficiently large number of red blood cells will be associated with other compounds (the red blood cell, in combination with glucose from food, forms glycated hemoglobin, which manifests itself differently in the analysis, similarly - other compounds).

When smoking or drinking strong drinks, a very large number of red blood cells with oxygen go into peripheral tissues, which also affects blood test results.