Prenatal Diagnosis of β Thalassaemia by Fetal Red Cell Enrichment with NH4Cl‐NH4HCO3 Differential Lysis of Maternal Cells

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Abstract
Summary. Prenatal diagnosis with globin chain synthesis analysis on fetal red blood cells concentrated by NH4Cl‐NH2HCO3 differential lysis of maternal cells (Ørskov lysis) was carried out in 27 pregnancies at risk for β thalassaemia and one at risk for sickle cell β0 thalassaemia. The β/γ globin chain synthesis ratio was also determined after anti‐i differential agglutination (12 cases), in almost pure fetal samples (six cases) and by extrapolation (one case). Differential lysis permitted the study of samples drawn by placental aspiration containing as little as 3.2% fetal red blood cells. There was no consistent difference between the β/γ ratios observed after differential lysis and those determined after the use of the other approaches. A presumptive diagnosis of homozygous β thalassaemia was made in nine cases. All but one of these pregnancies was terminated. The absence of β chain synthesis was confirmed by the study of fetal blood after abortion in four cases with suitable samples. Of the remaining pregnancies, six proceeded to term and non‐homozygous infants were delivered. The others are still in progress. No fetal loss occurred. ørskov lysis seems to be a very reliable method for prenatal diagnosis of β chain abnormalities. Moreover it can minimize the number and duration of placental aspirations required and thus the risk to the fetus.