Institute of Hematology, Royal Prince Alfred Hospital, Camperdown, NSW, Australia

Using the principle of different red cell antigen(s) between fetus and mother, foeto-maternal hemorrhage detection can be archieved by applying a fluorescence-tagged anti-human globulin to the corresponding antigen-antibody complex through flow cytometry. This has been proven successful in Rh(D) negative mother with a Rh(D) positive fetus. However, this method needs prior knowledge of maternal as well as fetal blood group. A similar method is developed by using anti-fetal hemoglobin antibody which reacts with the fetal hemoglobin containing cells after red cells are fixed and permeabilised. Although most normal adults have a few red cells containing Hemoglobin (HbF) and most pregnant women have an increased number of these cells, they can be differentiated by gauging the intensity of fluorescence produced. Exceptions can be seen in transfusion-dependent patients with β-thalassaemia.

A series of 32 specimen were prepared consisting of Rh(D) negative blood spiked with varying amount of Rh(D) positive cord blood. These samples were tested by the flow cytometry using anti-D and anti-fetal hemoglobin antibody respectively and also by Kleihauer Test. For Kleihauer versus anti-D, the Pearson correlation coefficient is 0.8176 (p<0.0001) and for anti-HBF versus anti-D the coefficient is 0.9939 (p<0.0001).