The quantification of fetomaternal hemorrhage by an enzyme-linked antibody test with glutaraldehyde fixation

A modified enzyme-linked antiglobulin test (ELAT) for quantifying D-positive red blood cells in the circulation of D-negative pregnant women is described. The antibody-antigen bond was stabilized and the problem of hemolysis eliminated by the use of 0.05% glutaraldehyde. The r value for the standardization curves for measuring cord RBC in mixtures was 0.98; coefficient of variation 5.8%. Reproducible quantitation of 0.125% D-positive cord RBC mixed with D-negative RBC was demonstrated. In comparative studies of artificial mixtures, Kleihauer-Betke results for more than 1% cord RBC were 50-100% greater than the true values. In several examples of large fetomaternal hemorrhages, the ELAT results matched the clinical data more closely than the Kleihauer-Betke based estimates. 2 ml of fetal RBC in a 1,600-ml red cell mass can be quantified using the modified ELAT.