- What is the reference value
- High RDW result
- Low RDW result
- When can the exam be requested
- How to prepare for the exam
RDW is the acronym for Red Cell Distribution Width , which in Portuguese means Distribution Range of Red Blood Cells, and which assesses the variation in size between red blood cells, this variation being called anisocytosis.
Thus, when the value is high in the blood count it means that the red blood cells are larger than normal, and very large and very small red blood cells can be seen in the blood smear. When the value is below the reference value, it usually does not have clinical significance, only if in addition to the RDW other indices are also below the normal value, such as VCM, for example. Understand what VCM is.
The RDW is one of the parameters that make up the blood count and, along with the other information provided by the exam, it is possible to check how the blood cells are producing and the person's general condition. When the RDW result is altered, it is possible to be suspicious of some situations, such as anemia, diabetes or liver problems, whose diagnosis should be made based on the analysis of the complete blood count and biochemical tests. See how to read the other blood count values.
What is the reference value
The reference value for RDW in the blood count is 11 to 14%, however, this result may vary according to the laboratory. Thus, if the value is above or below that percentage, it can have different meanings and, therefore, it is always important that the value is evaluated by the doctor who ordered the test.
High RDW result
Anisocytosis is the term that occurs when the RDW is increased, and a large variation in size between red blood cells can be seen in the blood smear. RDW may be increased in some situations, such as:
- Iron deficiency anemia; Megaloblastic anemia; Thalassemia; Liver diseases.
In addition, people undergoing chemotherapy or some antiviral treatment may also have increased RDW.
Low RDW result
The low RDW usually does not have clinical significance when interpreted in isolation, however, if other changes are seen in the blood count, it may indicate anemia caused by chronic disease, such as liver disease, kidney problems, HIV, cancer or diabetes, for example.
When can the exam be requested
This test is often requested when anemia is suspected, as symptoms such as dizziness, tiredness or pale skin appear, for example. Check out the main symptoms of anemia.
However, the doctor may also order the test when you have or have had:
- Family history of blood changes; Hemorrhage during surgery or after a stroke; Diagnosis of a disease that can cause changes in blood cells; Chronic disease, such as HIV.
Sometimes, this test can even be ordered in a routine blood test, without a specific cause.
How to prepare for the exam
In order for the blood count to be made and, consequently, the RDW is not necessary to fast. However, a complete blood count is usually required along with other blood tests that require fasting for at least 8 hours.
Blood collection usually takes less than 5 minutes and is easily done at the hospital or any testing clinic with the removal of a small blood sample through the vein.
