What Is the Definition of RDW-SD?

Q:
What is the definition of RDW-SD?

A:
Red cell distribution width (RDW) is a red blood cell parameter that measures variability of red cell volume/size (anisocytosis). According to different types of the hematology analyzer instruments, RDW can be reported statistically as coefficient of variation (CV) and/or standard deviation (SD), RDW-CV and/or RDW-SD, respectively.

RDW-SD takes measurements in “fL” and basically measures the width of red cells size distribution histogram–it calculates the width at the 20% height level of the histogram.

Here is a chart providing the clearer visual explanation.

The normal range of RDW-SD is 39-46 fL.

Keywords: rdw-sd definition

* The Content is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition.