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General Practice 2023

RDW: what é and because it can be high or low

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RDW: what é and because it can be high or low
RDW: what é and because it can be high or low

RDW is the acronym for Red Cell Distribution Width, which in Portuguese means Red Blood Cell Distribution Amplitude, and which evaluates the variation in size between red blood cells, this variation being called anisocytosis.

That way, 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 on the blood smear. When the value is below the reference value, it usually has no clinical significance, only if, in addition to the RDW, other indices are also below the normal value, such as the MCV, for example. Understand what VCM is.

The RDW is one of the parameters that make up the blood count and, together with the other information provided by the exam, it is possible to check the production of blood cells and the general condition of the person. When the RDW result is altered, it is possible to suspect some situations, such as anemia, diabetes or liver problems, whose diagnosis must be made from the analysis of the complete blood count and biochemical tests. See how to read the other values of the CBC exam.


When the exam is indicated

This test is often requested when anemia is suspected, due to symptoms such as dizziness, tiredness or pale skin, for example. However, the doctor can also order the exam when you have or have had:

  • Family history of blood disorders;
  • Bleeding during surgery or after a blow;
  • 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 there being a specific cause.

How to prepare for the exam

To have the blood count performed and, consequently, the RDW, it is not necessary to perform fasting. However, the blood count is usually ordered along with other blood tests that require a fasting period of at least 8 hours.

Blood collection typically takes less than 5 minutes and is easily done in the hospital or any testing clinic by removing a small sample of blood through the vein.

What does the result mean

The reference value for RDW in the blood count is 11 to 14%, however, this result may vary depending on the laboratory. Thus, if the value is above or below this percentage, it may have different meanings and, therefore, it is always important that the value be evaluated by the doctor who ordered the exam.

High RDW

Anisocytosis is the term given 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;
  • Thalassaemia;
  • Liver diseases.

In addition, people undergoing chemotherapy or taking an antiviral drug may also have increased RDW.

low RDW

Low RDW usually has no clinical significance when interpreted alone, however if other changes in the blood count are verified, it may indicate anemia caused by chronic disease, such as liver disease, kidney problems, HIV, cancer or diabetes, for example. example.

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