Direct enzyme linked antiglobulin tests (ELAT) for detecting in-vivo sensitized erythrocytes: evaluation of screening for abo incompatibility of newborn

Abstract

ABO incompatibility of the newborn is one instance where immune hemolysis may present with a negative direct antiglobulin test (DAT) and therefore a simple sensitive test for detecting sensitization would be useful in this clinical situation. To evaluate the usefulness of ELAT in detecting in-vivo sensitized red cells, 1608 maternal-baby pairs were screened for ABO incompatibility over a period of 10 mth. Of 251 ABO-incompatible babies, there were 49 (19.5%) with positive DAT, but an additional 67 (26.7%) were ELAT positive. These were eluate positive as well, indicating that the increased number with sensitized cells as shown by ELAT is due to detection of in-vivo sensitized cells. The positive predictive value for ABO hemolytic disease of the newborn (HDN) is 48%, which is two times that of DAT. Calculating the difference of the absorbance from baseline (delta OD) may give an indication of degree of sensitization which together with the maternal antibody titre would aid us in the estimation of antigen dosage on the baby's red cells and in the appraisal of the role of antigen dosage in HDN.