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. The erythrocyte distribution width (RDW) test is used to determine whether there are size differences in the distribution of erythrocytes in the blood, which has the most important role in this mechanism.
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.
RDW (erythrocyte distribution width) is also evaluated with different tests with different interpretations of the sizes of erythrocytes. The main ones are RDW-CV and RDW-SD.
The RDW-CV reports the difference between the largest red cell volume and the smallest red cell volume. The RDW-CV is found as a ratio over percentile by dividing the width of the red blood cells in the histogram at one standard deviation by the MCV (mean red cell volume). It is also expressed as the coefficient of variation of erythrocyte distribution width. The normal value of RDW-CV does not exceed 14%. RDW-CV may not reflect the true change in red cell size as it depends not only on the mean volume of red blood cells but also on the width of the distribution curve.
Since RDW-CV shows differences in diameter (anisocytosis) of erythrocytes, it is used in the differential diagnosis in cases where anisocytosis is prominent and especially in anemia with microcytosis. For example, while RDW-CV is increased in iron deficiency anemia, it is normal in beta thalassemia carriers.
A high or low RDW-CV value may be a sign of serious diseases. The RDW-CV test detects immature large erythrocytes or mature small erythrocytes in the body and diagnoses the diseases they cause. The large size difference between erythrocytes causes a high RDW-CV value. When the production activation in the bone marrow increases, the RDW-CV value also increases.
Table of contents
RDW-CV Normal Values:
The RDW-CV test is not done alone. This test is done in conjunction with the RDW-SD test. The normal value ranges for both tests are as follows.
RDW-CV
11.9-14.5% in women
11.8-14.6% in men
RDW-SD
29-46 fl in men and women
RWD-CV height:
Blood RDW-CV is usually done in conjunction with the MCV test. Patients with RDW-CV elevation usually present with weakness, coldness and numbness in the hands and feet, dizziness, jaundice, hair loss, forgetfulness, and nail breakage. Patients with elevated RDW-CV may require medical intervention and may face more serious problems such as shortness of breath due to lung damage, heart enlargement, liver failure, and cancer in the future.
Reasons for low RDW-CV:
- Iron deficiency anemia and other anemias
- Vitamin B6 deficiency
- Thalassemia
- Joint inflammation
- Hemoglobin E disease
- Bleeding
Possible situations according to the relationship between RDW-CV and MCV values:
- Macrocytic anemia if RDW-CV is low and MCV is high
- Microcytic anemia if RDW-CV is low and MCV is low
- If normal RDW-CV and MCV are low:
- Hemoglobin E disease
- Chronic anemia
- If normal RDW-C and MCV are high:
- Aplastic anemia
- Chronic liver disease
- Receiving chemotherapy
- If RDW-CV is high and MCV is normal:
- Sickle cell anemia
- Iron deficiency anemia
- Liver disease
- If RDW-CV is high and MCV is low:
- Sickle cell anemia
- Iron deficiency anemia
- If RDW-CV is high and MCV is high:
- Folic acid deficiency
- B12 Deficiency
- Hemolytic anemia
- Myelodysplastic syndrome (bone marrow disease)
- Chronic liver disease