Prenatal diagnosis of beta-thalassemia using selective hemolysis of maternal cells contaminating fetal blood sample.

The prenatal diagnosis of the severe, hereditary anemias may be impossible when a placental blood sample which contains a high percentage of maternal rather than fetal cells is obtained. An incubation system described by Boyer et al. [3] with minor modifications, was applied to mixtures of blood from prematures and adults in order to increase the proportion of premature cells. After 40 min incubation, 95% or more of adult red cells were destroyed, whereas 30-60% of premature red cells were recovered, as determined by several independent methods. In a pregnancy at risk for beta-thalassemia, a placental blood sample which was purely fetal was obtained. Complete lack of in vitro beta-globin synthesis showed the fetus to have homozygous beta-thalassemia. When fetal blood was mixed with maternal blood in a ratio of 1:15, beta-globin synthesis in the mixture was comparable to that of normal fetuses. In contrast, when the cell mixture was subjected to selective hemolysis prior to separation of globins, beta-globin synthesis again was not detectable. Thus, using selective hemolysis, the correct diagnosis could be established from a blood sample containing only about 6% of fetal cells.