Change in red blood cell distribution width with iron deficiency.

Red cell volume distribution width (RDW-CV) was examined as a means of diagnosing iron deficiency. Iron deficiency was classified as iron deficiency anaemia, prelatent or latent iron deficiency in 1648 students. MCV and RDW-CV (mean +/- ISD) in each group were 89 +/- 4 ft, 12.7 +/- 0.7% in normal individuals, 89 +/- 4 fl, 13.2 +/- 0.8% in prelatent deficiency, 86 +/- 6 fl, 14.0 +/- 1.5% in latent deficiency, and 79 +/- 7 fl, 15.6 +/- 1.7% in iron deficiency anaemia, respectively. Although microcytosis was evident only in iron deficiency anaemia, RDW-CV showed larger values concomitant with the development of iron deficiency. The sensitivity of RDW-CV for the diagnosis of iron deficiency anaemia was 77.1%, and for iron deficiency anaemia and latent deficiency 49.2%, the specificity being 90.6%. In countries with a high prevalence of iron deficiency and low thalassaemia, iron deficiency should be screened by RDW-CV determination without serum iron or ferritin measurements.