Hemoglobin content of single erythrocytes from fetuses with parents having heterozygous beta-thalassemia.

The hemoglobin content of single erythrocytes was determined by microspectrophotometry as total extinction (TE) at 415 nm in subjects with a wide spectrum of hemoglobin levels and erythrocyte indices. Precise measurements of the cellular area (A) and the ratio TE/A were also recorded. A significant correlation was found between TE and mean corpuscular hemoglobin (MCH), A and mean corpuscular volume, and TE/A and mean cell hemoglobin concentration (MCHC) for the cases studied. In addition, TE, A and TE/A were determined in fetal erythrocytes obtained by fetoscopy at the 20th week of gestation for prenatal diagnosis of beta-thalassemia. The mean red cell TE and TE/A of the group of fetuses diagnosed to have thalassemia major were significantly lower than those of the group of normal controls and with heterozygous beta-thalassemia. The significant differences of TE, A and TE/A between maternal and fetal blood allowed a safe distinction of the latter. The calculated MCH of the fetuses with thalassemia major was 12% less than that of the normal controls; the respective difference of the mean cell size was 5% and that of MCHC 3% lower than normal.