Red blood cell volume distribution parameter

Red blood cell volume distribution parameter

(Red Cell Distribution Width, RDW)

RDW parameter expresses the distribution range of red blood cell volume

The parameter of size changes is reported in terms of standard deviation (RDW-SD) and coefficient of variation of RDW-CV

The reference range of RDW – SD is between 39 – 47 femtoliters
{ normal value 42 (+ , – ) 3 }

and it is equal to the width of the line that intersects the histogram of red blood cell volume from 20 percent frequency and represents the difference in the volume of the largest and smallest red blood cell at 80 percent frequency

The higher this range is, the greater the variation in red blood cell size. This parameter is obtained from the volume histogram

For example, if this line intersects the right side of the curve at the 111 femtoliter position and the left side at the 70 femtoliter position, RDW – SD is equal to
111 – 70 = 41 femtoliters

To calculate the RDW-CV parameter, the value of one standard deviation of RDW is divided by MCV and the result is multiplied by 100. The normal value of RDW-CV is between 11.5 and 14.5 percent.

Note: Care must be taken in interpreting RDW-CV
If the standard deviation of RDW-SD increases due to size variation and the volume increases at the same time, the value of RDW-CV becomes normal despite size changes (anisocytosis).

A normal deviation width with uniform blood cells, but with a decrease in the average volume, leads to an increase in RDW-CV. In these cases, viewing the histogram is helpful.

Note: RDW parameter indicates changes in red blood cell size and **the value of this parameter in terms of SD is more accurate than CV**
Because RDW-SD is obtained directly from the volume histogram

Based on MCV and RDW, red blood cells can be classified, for example MCV is equal to 70 and 20% = RDW means non-uniform microcyte and is one of the morphological patterns in iron deficiency

or MCV = 110 and RDW = 18% means non-uniform macrocyte, which is often seen in megaloblastic anemia

or MCV = 70 and RDW = 12% means a single-handed microcyte, which may indicate thalassemia syndromes

The RDW parameter is not only valuable in the classification of anemias, but its increase without association with anemia in many diseases indicates the chronicity of the disease and the possibility of death due to it, for example, the increase of RDW in chronic failure The kidney indicates a decrease in filtration and its increase in heart patients indicates a failure in blood supply and its increase in diabetic patients indicates an increase in the risk of kidney failure and vascular complications.

An increase in RDW in old age is a predictor of mortality due to the complications of this age, therefore an increase in RDW is a predictor of criticality for all cases of mortality.

Drawing the median line intersects the X-axis in the volume histogram at the MCV value, the width of the line that intersects the volume histogram at 20% frequency, is considered as the RDW-SD parameter
The value of RDW – SD is approximately equal to three standard deviations (3SD).

To calculate RDW in terms of CV, the value of 1SD width is divided by MCV and the result is multiplied by 100.

This post is written by jm30303030