Relevance of red cell distribution width (RDW) in the differential diagnosis of microcytic anaemias.

The authors studied the red cell distribution width (RDW) index (obtained by Coulter Counter S Plus IV) in normal subjects and in patients with beta-thalassaemia trait and iron deficiency anaemia. Statistics and reference limits for the above three conditions are given. In order to make a differential diagnosis between beta-thalassaemia trait and iron deficiency anaemia, linear discriminant analysis was carried out. Global correct classification was 91.5% on our first sample of patients and 88.8% on a subsequent validation sample of microcytic patients. The percent of correct beta-thalassaemia trait diagnoses was 94.4% and 86.7% for the first and validation samples respectively. For iron deficiency anaemia correct diagnoses of 86.2% and 90.9% were achieved.