Red cell distribution width

Keywords: RDW

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.