Incidence of ABO haemolytic disease of the newborn in a group of Hong Kong babies with severe neonatal jaundice.

Two methods were used to determine the incidence of ABO haemolytic disease of the newborn (ABO-HDN) among Hong Kong Chinese infants. The first method employed the Lui elution technique to elute anti-A,B from cord blood of Group A and B babies with a Group O mother, and set out to correlate the titration score of the eluate with the serum bilirubin of the neonates. This method proved to be a failure because of the poor correlation. The second method was mathematical. By comparing the 'expected' frequency of various mother-infant ABO combinations (based on the ABO distribution of our local population) with the 'observed' frequency of a cohort of infants with severe neonatal jaundice, it was found that only two combinations (O-A and O-B mother-infant pairs) were responsible for ABO-HDN, for which the incidence was 1 in 5 among infants with a serum bilirubin level of 300 mumols/L or more.