Red cell distribution width (RDW)

Last updated: Thursday, 25, March, 2004

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Item Process
Specimen

5 mL blood in EDTA tube.

2 mL blood in special paediatric EDTA tube.

Method

Part of FBC on many automated instruments.

Reference Interval

Varies with instrument - consult laboratory.

Application

The RDW may assist in the classification of anaemia, in association with the blood film, and the other red cell indices (MCV, MCH and MCHC).

Interpretation

Quantitative assessment of the degree of variation in red cell size/volume (anisocytosis).

Reference

Brittenham GM and Koepke JA. Arch Pathol Lab Med 1987; 111: 1146-1148.