What is the meaning of the RDW value?
Doctors refer to the RDW value (Red Blood Cell Distribution Width) as the erythrocyte distribution width (EVB). It indicates how and with what volume the red blood cells are distributed in the blood. Doctors call these erythrocytes . As a rule, they do not change in size during their lifetime. The RDW value, in connection with the volume and size of the red blood cells, is an important indicator of the presence of a disease.
The RDW value provides information about the condition of the red blood cells
The doctor determines the erythrocyte distribution width as part of the blood count. This EVB or RDW value indicates the distribution of the erythrocytes according to size and volume. Red blood cells usually stay the same size throughout their lifespan. The normal EVB is less than fourteen percent. An increased RDW value reflects greater variability in erythrocyte size. The value allows an anisocytosis of the erythrocytes to be identified. Anemia often causes an altered erythrocyte distribution width.
Standard values for the RDW value
The standard values for the number of red blood cells in the blood differ according to gender. In women the number is 4.1 to 5.1 million per microliter, in men 4.2 to 5.6 million per microliter. The standard value for the RDW is 11.5 to 14.5 percent. The value indicates the deviation of the erythrocytes from the normal size.
How does the doctor determine the RDW value?
The doctor determines the erythrocyte distribution width as part of the blood count using EDTA blood. The RDW value is the unit of measurement for the size distribution of the erythrocytes. The doctor gives it as a percentage. The measurement is carried out using flow cytometry. The calculation of the EVB results from the standard deviation of the volume (S V ) of the red blood cells and the mean of the erythrocyte volume (MCV). The doctor uses the formula: EVB (%) = (S V * 100) ÷ MCV.
Distribution area of erythrocytes
The red blood cells are six to nine micrometers in diameter and one micrometer thick at the center of the erythrocyte. Peripherally, the thickness is two micrometers. The red blood cells are distributed according to the Gaussian distribution. At 7.5 microns, there are a maximum of about 120 to 500 cells . The RDW value depends on the diameter of the red blood cells and correlates with their thickness. The erythrocyte distribution width provides information about strong shape and size differences of the red blood cells (anisocytosis). The normal values are 11.5 to 14.5 percent.
What diseases are present if the RDW value is too high or too low?
Physicians examine the erythrocyte distribution width in suspected anemia (hemolytic anemia, iron deficiency anemia, pernicious anemia or globule cell anemia). In this disease, the organism has too little hemoglobin, too little hematocrit or too few red blood cells in the blood. Anemia is accompanied by the disease-specific symptoms of tachycardia, fatigue, shortness of breath, breathing difficulties, brittle and deformed nails (watch glass nails), discoloration of the skin and a noticeably reduced physical resilience.
The causes are:
- infections
- a lack of iron, folic acid and vitamin B 12 ,
- a tumor,
- an existing liver cirrhosis or kidney disease,
- Alcoholism,
- a high blood loss due to accidents or bleeding in the gastrointestinal area,
- pregnancy and lactation.
If the reference range is significantly exceeded, the doctor concludes that it is osteomyelofibrosis (bone marrow fibrosis). In the study “Red cell distribution width: an inexpensive and powerful prognostic marker in heart failure” by Al-Najjar Y. et al. scientists pointed out that the RDW value also serves as a marker for early detection of colon cancer and inflammatory bowel diseases such as ulcerative colitis (colitis).
In addition, researchers of the study “Relation Between Red Blood Cell Distribution Width and Cardiovascular Event Rate in People With Coronary Disease” by Tonelli M. et al. related the RDW to cardiovascular disease.
What happens if the doctor finds a deviation?
Physicians only see elevated values in the context of other laboratory values. The individual value is not meaningful enough to determine a disease with certainty. Low RDW values have no clinical relevance in everyday life. To determine anemia, the doctor also uses MCH, MCHC and MCV values.
What to do if there is anemia?
In addition to the RDW value, the doctor determines other blood values to determine anemia. He clarifies the cause of the anemia and designs a therapy that he adapts to the patient. For support, the person concerned pays attention to an iron-rich diet in order to increase a reduced RDW value. Iron supplementation helps women who experience anemia from heavy menstrual bleeding. It also ensures a constant RDW. Before patients resort to self-medication, it is advisable to consult their family doctor.
Medical note for our readers:
Our patient information explains medical topics in a simple and understandable way. Our information is not a substitute for a medical examination. Please see a specialist for diagnosis or treatment.
