Red Cell distribution Width (RDW)

by: Joe Hing kwok Chu

The RDW is a standard part of the complete blood count.

When blood cell counts are being done with electronic instruments, the pulses produced by the RBC can be measured.  The height of these pulses is proportional to the size.

RDW is a measurement of the variability of red blood cell size. Higher numbers indicate greater variation in size.

The normal range for the red cell distribution width (RDW) is 11.5 - 14.5 %.

Clinical Implication:

A high RDW with a normal MCV points to deficiency of  iron, B₁₂ and folate.

Transferrin saturation and serum ferritin determinations test should follow the findings.

Absence of thalassemia or an acute disease of red cell fragmentation, an elevation of RDW may reflect reticulocytosis due to blood loss, most likely from GI tract.

Note:

Reticulocytosis is a condition of increase number of reticulocytes, usually occurs in anemia.  Reticulocytes are immature red cells that appear during regeneration of loss blood.

Elevatedserum transferrin saturation, more than 2% of the adult US population, were
at increased risk for all-cause mortality. [1]  Low level indicates that the iron is low.

[1] Annual of Family Medicine 2004;2:133-138. DOI: 10.1370/afm.25.
 

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