Intended Use

The detection of fetal erythrocytes in the maternal circulation was first described in 1957 by Kleihauer and associates. The passage of erythrocytes from an Rh positive fetus into the circulation of an Rh negative mother results in the formation of specific Rh antibodies. In subsequent pregnancies, the Rh antibodies formed in the blood serum of the Rh negative mother are readily transmissible through the placenta into the circulation of the fetus. The action of the antibodies on the Rh positive cells of the fetus may result in a disease entity recognized as isohemolytic disease, or erythroblastosis.

Rh negative mothers who have been sensitized to the Rh factor as a consequence of transfusion with Rh positive blood from the fetus are administered specific gamma globulin containing anti Rhₒ(D) to suppress the immune reactions. The amount of gamma globulin administered is calculated by assessing the magnitude of fetal/maternal hemorrhage.

The procedure described herein is a modification of that described by Clayton, et al whereas blood smears, which have been properly dried and fixed, are immersed in a citrate/phosphate buffer, pH3.2. Adult hemoglobin (HbA) dissolves out of the cells, whereas fetal hemoglobin (HbF) which is acid resistant, remains intracellular and is stained and enumerated by microscopic examination.