RDW Test
The free oxygen that passes into the blood through the lungs is stored in the blood by the erythrocytes and transported to the tissues, and the carbon dioxide in the tissues is delivered back to the lungs. Whether there are size differences in the distribution of erythrocytes in the blood, which has the most important role in this mechanism, is revealed by the RDW test of erythrocyte distribution width.
Normally, mature erythrocytes in the blood are expected to be the same size. As the size of the erythrocytes changes, both their capacity and functions will be affected, which can cause many diseases. In addition, many diseases cause these size differences and realize their symptoms. For example, before anemia appears in the blood, the size of the erythrocytes (RWD value) begins to increase. Because less production of young erythrocytes causes an increase in the number of mature erythrocytes and a relative increase in erythrocyte sizes. While RWD is normal in thalassemia carrier, RWD value increases in iron deficiency anemia. RDW values are used to evaluate many medical conditions, including anemia.
If patients have symptoms of anemia such as dizziness and fatigue, the RDW value can be examined. With this examination, the cause of anemia is tried to be determined. In addition, RDW value can be examined in order to evaluate the condition of thalassemia patients, to analyze the risk of iron deficiency anemia in pregnant women, and to analyze other conditions in the blood that may cause anemia in the early period. Erythrocyte distribution width can sometimes be confirmed by peripheral smear. RDW values can also be examined to define the prognosis of some diseases. For example, RDW value is one of the important prognostic tests in the course of heart failure. The clinical use of RDW is not limited to anemia causing microcytic anemia. It is also used to differentiate iron deficiency anemia from thalassemia and other hemoglobinopathies. In addition, RDW elevation can also be evaluated in conditions that cause ischemic heart disease, acute and chronic heart failure, atherosclerosis, vascular occlusive disease, hypertension, active state of inflammatory bowel disease, rheumatoid arthritis and generally progressive inflammation. It has been shown that inflammation and oxidative stress affect RDW, and RDW also reflects the increase in hepcidin, IL-6, TNF-alpha and other cytokines circulating in the blood.
RDW value is usually not used alone and MCV, MCH, Hgb, Hct are interpreted together with other erythrocyte evaluation indices. For RDW, in tests calculated as a percentage, the normal value is 13 ± 1.5%. This value is found as 15-25% in iron deficiency anemia, 12-15% in thalassemia carriage, and 25-35% in thalassemia major. The RDW value can be found to be 17-20% in hereditary spherocytosis, and 20-25% or even higher in congenital dyserythropoietic anemia. RDW values above 25% overlap with sideroblastic anemia.
Some diseases with normal RDW values:
- Homogeneous microcytic, normocytic and macrocytic anemias
- Thalassemia
- Chronic diseases
- Chemotherapy
- Chronic liver disease
- Nonanemic hemoglobinopathy
- Chronic myelocytic leukemia
- Bleeding
- Aplastic anemia
- Preleukemia
- Hypothyroidism
- Alcoholism
- Nutritional disorders
Some diseases with increased RDW value:
- Hereditary spherocytosis
- Heterogeneous microcytic, normocytic and macrocytic anemias
- Iron deficiency
- Early stage of iron and folate deficiencies
- Folate and B12 deficiency (Megaloblastic anemia)
- S Beta thalassemia
- Hemoglobinopathies (SS, SC)
- Immune hemolytic anemia
- Hemoglobin H disease
- Myelofibrosis
- Presence of cold agglutinin
- Erythrocyte breakdown
- Sideroblastic anemia
- Nutritional disorders
The RDW value is high in mixed anemia with more than one cause. RDW values can also be used for other analyzes in individuals without any signs of anemia. For example, people with a high RDW have a higher risk of death. It has been observed that conditions with a high RDW value in patients with heart disease or cancer diagnosis have a worse prognosis.
High RDW value in people who lose weight for no reason increases the possibility that weight loss is due to any cancer. The RDW value is used in sleep disorders, in people at risk of diabetes, in risk analysis before surgery or in the evaluation of the course of autoimmune diseases.