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RDW blood test

Red blood cell (RBC) indices are calculations derived from the complete blood count that helps in the process of diagnosis and classification of Anemia. A RBC indices blood test requires 3 to 5 ml of blood collected from a vein puncture.

RDW (Red cell Distribution Width) blood test that calculates any variation in size of RBC. Normally Red Blood Cells are of a standard size. Since RBCs tend to get smaller and rounder as they age, it is not possible for all cells to be exactly the same size. RDW test determines the changes in the volume of the cells in the red cell population. The variations pertaining to the size of the red blood cells is called Anisocytosis and the shape is called Poikilocytosis.

The incidence of these conditions and the detection of abnormal or varied red blood size are determined by diagnostic blood smear analysis and also through automated analyzers.

The following are the normal results for red blood cell indices ( a measurement of the variation in size of red blood cells):

  • Mean Corpuscular Volume (measure of the average volume of a RBC) : MCV 82-98 femtoliters (fl)
  • Mean Corpuscular Hemoglobin Concentration (measurement of the average concentration of hemoglobin in a RBC) : MCHC 33-37 g/dl
  • Mean Corpuscular Hemoglobin (Measurement of the average weight of hemoglobin in a RBC): MCH 26-34 picograms (pg)
  • RDW 11.5-14.5%

Normochromic: Indicates a normal concentration of hemoglobin. The RDW increases in anemia caused by deficiencies of Vitamin B12, iron or folic acid. Abnormal hemoglobin, as in sickle cell anemia, can result in changes in the shape of red blood cells. In addition it may also cause them to hemolyze. The abnormal shape and the cell fragments as a result of hemolysis would tend to increase the RDW. Severe blood loss may also induce immature cells into the blood that can increase the RDW.

Possible causes of abnormal MCV: MCV (Mean Corpuscular Volume) is an index of the size of the RBC. When the MCV is below normal, the RBC will be smaller than the normal size - which is known as microcytic. On the other hand, if the MCV is higher than normal, the RBC will also be larger than normal which is called as macrocytic while the normal RBC size is termed as normocytic.
High MCV: Macrocytic anemia owing to vitamin B12 and folic acid deficiency

Low MCV: Microcytic anemia, Thalassemia, poor iron content in diet and chronic illness

Normal MCV: Normocytic anemia owing to liver,kidney diseases, bone marrow disorders, hemolysis (distruction of red blood cells) or excessive bleeding

A low MCH (Mean Corpuscular Hemoglobin) is an indication that RBCs have too little hemoglobin. When viewed under the microscope, the RBCs appear pale and hence called as hypochromic. The MCHC (Mean Corpuscular Hemoglobin Concentration) is the ratio of RBC's hemoglobin mass to the cell volume. MCHC is elevated in hereditary Spherocytosis - as a result of the structural protein defect in the RBC.

RDW Blood Test - illustration of typical Red Blood Cells

Calculating Red Blood Cell Distribution: The determination of red cell distribution width is mathematically expressed as Red cell distribution width = (Standard deviation รท Mean cell volume) X 100.

Conditions such as pernicious anemia cause changes in RBC size. Often there is variation in shape too. This can be detected by changes in RDW. Normal RDW range is 11 - 15%. Higher RDW is indicative of disorders such as anemia. RDW blood test is often conducted along with MCV blood test to check the exact cause.

Hemolytic Anemia

Hemolytic anemia is a kind of anemia that occurs when there is high rate of destruction of RBC. Infections of Streptococcus or other conditions can lead the body to destroy its own RBC. Hemolytic anemia can enlarge the spleen that results in increased destruction of red blood cells (Hemolysis). Some complications of this Anemia:

Persons suffering hemolytic condition might experience severe fatigue, dizziness, shortness of breath and chest pain. A complete blood count can help in identifying hemolytic anemia. Hemolytic anemia is treated with lifestyle changes and medicines. In more severe cases blood transfusion and plasmapheresis might be resorted to.

Autoimmune Hemolytic Anemia : Warm antibody hemolytic anemia, one of the most common types afflicting women, results when the body produces auto antibodies that coat red blood cells which in turn are destroyed by the spleen, liver or bone marrow. Many of these patients also have leukemia, lupus, lymphoma or connective tissue disease. In cold antibody hemolytic anemia, the body targets red blood cells at or below normal body temperature - often to patients who have had pneumonia, mononucleosis or other acute infections. Exposure to cold temperatures can accelerate red blood cell destruction resulting in fatigue, discoloration of limbs and joint pains.

Sideroblastic Anemia: In this anemia, the body has sufficient iron but it fails to incorporate it into hemoglobin.


Anemia stands for 'without blood' in Greek; When the number of red blood cells (RBC) falls below normal, Anemia is a resultant condition. Hemoglobin is an important constituent of RBC. Hemoglobin usually occurs in the range of 12 and 18 g/dL (grams per deciliter of blood). If the hemoglobin levels show a decrease, anemic conditions set in. Consequently, the various organs and tissues of the body do not receive adequate oxygen on account of the diminished oxygen carrying capacity of the blood. This impairs their normal functioning. Usually women have smaller stores of iron than men. Besides, they also lose blood during menstruation making them primary targets for anemia.

Red Blood Cells

World Health Organization (WHO) defines anemia as a hemoglobin level lower than 13 g/dL in men and lower than 12 g/dL in women. It is essential to be familiar with the typical symptoms of anemia. Often anemia is misdiagnosed and left untreated. An anemic person is likely to feel extremely tired and weak. This is accompanied with dizziness and breathlessness. A person suffering from anemia tends to appear pale and experience feelings of depression. In some cases, anemia can lead to heart ailments too.

Causes of Anemia

  • Serious disease or infection such as hookworm infection, bleeding piles, esophageal var ices and peptic ulcers.
  • Hemorrhagic - Excessive blood loss due to surgery, menstruation or injury.
  • Genetic defects lead to sickle cell anemia, Thalassemia anemia and aplastic anemia.
  • Hemolytic - Excessive intravascular blood destruction where red blood cells are destroyed prematurely.

Types of Anemia

Iron deficiency Anemia - Nearly 20% adult women tend to suffer from this form of anemia. Loss of blood due to menstruation is not compensated with an iron-rich diet. Pregnancy and breast feeding can also deplete iron stores. Iron deficiency anemia is also noticed during growth spurts or internal bleeding.

Aplastic anemia - When the bone marrow does not produce sufficient quantities of blood cells, aplastic anemia is noticed. Childhood cancers such as leukemia are often responsible for this form of anemia. Other possible causes of aplastic anemia are radiation, cancer or antiseizure medications and chronic diseases such as thyroid or kidney malfunction. Treatment for aplastic anemia involves blood transfusions and bone marrow transplant. This is done to replace malfunctioning cells with healthy ones.

Vitamin deficiency anemia - Low levels of folic acid lead to faulty absorption of iron. Anemia caused due to folic acid deficiency is called Megaloblastic anemia. Pregnancy doubles the body requirements of folic acid and it is imperative that pregnant women take folic acid supplements. Good dietary sources of folate are fresh fruits, green leafy vegetables, cruciferous vegetables, liver and kidney, dairy products and whole grain cereals. Vegetables should be eaten raw or lightly cooked.Folic acid anemia is also a common problem faced by alcoholics. Vitamin B-12 deficiency can lead to a condition of Pernicious anemia. Diseases such as thyroid malfunction or diabetes mellitus can affect the body's ability to absorb vitamin B-12. This vitamin is vital in the production of hemoglobin.

Vitamin C Deficiency Anemia is a rare form of Anemia that is the result of small red cells owing to prolonged dietary deficiency of the Vitamin C.

Sideroblastic Anemia: In this anemia, the body has sufficient iron but it fails to incorporate it into hemoglobin.

Hemolytic Anemia results from high rate of destruction of Red Blood Cells (RBC) at a rate faster than the rate bone marrow can replenish them.

Thalassemia anemia - Thalassemia or Cooleys Disease is a hereditary disorder found predominantly in people of South East Asian, Greek and Italian racial groups. This form of anemia is seen in differing degrees as Thalassemia encompasses a group of related disorders that affect the human body in similar ways. The most common occurrences of Thalassemia are alpha and beta thalassemia. Alpha thalassemia occurs when there are defects in the genes that produce alpha globin, while beta thalassemia occurs when there are defects in the genes that produce beta globin. The severity of the disorder depends on how many genes are affected and the specific mutations involved. Thalassemia anemia is characterized by symptoms like jaundice, enlarged spleen, shortness of breath and facial bone deformities.
Thalassemia is a group of inherited blood disorders that affect the production of hemoglobin, a protein in red blood cells that carries oxygen throughout the body. The disorder is caused by mutations in the genes that control the production of hemoglobin. Thalassemia anemia occurs when a person has fewer red blood cells than normal, or the red blood cells are smaller and do not contain enough hemoglobin. This can lead to a range of symptoms, including fatigue, weakness, pale skin, jaundice, and an enlarged spleen.

Treatment for thalassemia anemia may involve blood transfusions, iron chelation therapy to remove excess iron from the body, and bone marrow transplant in severe cases. With appropriate treatment and management, many people with thalassemia can lead healthy and productive lives.

Diagnosing Anemia

A complete blood count test will test for hemoglobin levels and display an anemic condition. But often anemia is a symptom whose cause lies deeper. The cause and type of anemia will determine the treatment that is needed. A stool test will help in detecting occult blood. Hemoglobin electrophoresis is a blood test that helps identify abnormal hemoglobins. Diagnosing thalassemia or sickle cell anemia becomes possible with this test.

Treating Anemia

Deficiency can be treated with supplements of iron, Vitamin B-12 and Vitamin C. Partaking an iron-rich diet can be beneficial for those suffering from nutritional deficiency anemia. Seafood, nuts, whole grains and dried fruits such as raisins, prunes and apricots are rich in iron. Ensure adequate consumption of Vitamin C as it aids and stimulates iron absorption. Try and combine citrus foods with iron-rich foods - add tomatoes to a turkey sandwich or chopped strawberries with iron-fortified breakfast cereals.

Tags: #RDW blood test #Hemolytic Anemia #Anemia
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Collection of Pages - Last revised Date: July 23, 2024