The low mean cell volume in routine haematology.

This study establishes the prevalence and distribution of an MCV less than 80 fl by review of the Coulter indices of 7887 samples. Retrospectively, 146 patients are studied and the relationships between the low MCV, film microscopy, iron status, and clinical diagnosis assessed. Plasma ferritin measured radioisotopically in 100 patients is compared to serum iron and iron binding capacity values and some of the problems of assessing iron stores are discussed. The discriminant formulae devised to differentiate between the microcytosis of thalassaemia trait and that or iron deficiency are found to be of limited value when applied to the red cell indices of a hospital population.