A new approach for the antenatal diagnosis of beta-thalassaemia: a double labelling immunofluorescence microscopy technique.

A new approach to the antenatal diagnosis of beta-thalassaemia major (homozygous beta-thalassaemia) has been developed. Using rhodamine-labelled antibodies directed against gamma-globin, fetal erythrocytes can be identified in fetal blood samples contaminated with maternal cells, and using fluorescein-labelled antibodies directed against beta-globin, the presence of beta-chains (and thus Hb-A) may be determined in the same cells by double labelling immunofluorescence microscopy. The results obtained using this technique on blood samples from fetuses at risk for beta-thalassaemia major show that if fetal beta-chains are detected immunochemically the fetus is normal or heterozygous for beta-thalassaemia and over 85% of the fetuses unaffected by beta-thalassaemia major may be identified in this way. The technique is rapid, applicable to small numbers of fetal erythrocytes heavily contaminated with maternal cells and eliminates the necessity of determining chain synthesis ratios in those cases where beta-chains are detected immunochemically.