Erythrocytic microcytosis: clinical implications in 100 patients

Hematology results from 3800 blood samples were examined for the presence of erythrocytic microcytosis. One hundred patients with electronically measured mean corpuscular volumes of 75 cubic microns or less were reviewed to determine the cause of microcytosis and evaluate recently described simplified techniques for separating thalassemia trait from other causes of microcytosis. The discriminant function formula of England and Fraser [MCV - RBC - (5 x Hgb) - 3.4] was found to be useful in uncomplicated patients with the Mediterranean type of thalassemia trait (betadegree) but less useful in the African type (beta+) of heterozygous beta-thalassemia. Anemias of chronic disorders were found to be a major cause of microcytosis. Microcytosis of no apparent cause was found in some children. Improved techniques in hemoglobin A2 quantification remain the best approach for detecting beta-thalassemia heterozygotes.