A rapid and accurate single-drop modification of the acid-elution technique for detecting fetomaternal hemorrhage

A single-drop modification of the acid-elution technique (Kleihauer-Betke) for quantitating fetomaternal hemorrhage is described. It obviates the need for the tedious and time-consuming manual counting of background adult cells. Rather, this is achieved by automated red-blood cell counting of the initial specimen and delivery of a standard volume (1 microliter) of a standard dilution (1:1,000) in the form of a droplet to a microscope slide. The droplet is left to dry undisturbed at room temperature and then stained. The fetal cells are manually counted while the total number of cells is calculated from the initial red-blood cell count, standard volume, and standard dilution. Determinations on 4 different concentrations of fetal/adult red cell mixtures are performed. Results indicate improved accuracy and precision relative to the standard technique in significantly less time for volumes of fetomaternal hemorrhage requiring more than the standard dose of Rho(D)-immune globulin.