Alloimmunization during pregnancy with special emphasis on anti-D : Laboratory and clinical management

Abstract: The laboratory and clinical management of alloimmunized in pregnancy has been investigated according to a protocol currently in use in Örebro region. A 12 year epidemiological study showed the prevalence of alloimmunization to be 0.57% in this Swedish populationwith a 0.24% incidence of clinically significant antibodies that can induce haemolytic disease of the newborn (HDN). Rh antibodies, predominantly anti-D, are still the causes of most cases of severe HDN in which 45/47 babies required exchange transfusion. During the studyperiod, 14 mothers were successfully treated with plasma exchange during pregnancy owing to high anti-D antibody concentrations. Only two other blood group syswms, Kell and Duffy, besides Rh affected newborns to alloimmunized mothers to such a grade that exchange transfusion of the newborns was necessary. All generally accepted for the fetus clinically nonsignificant antibodies were also followed and shown not to cause HDN. In 3 instances, anti-D was detected in partial RhO-positive mothers who were carrying normal RhO-positive fetuses,a study to identify these partial RhD individuals and to group them into D-categories was performed. The ability of the indirect antiglobulin titre (IAT), AutoAnalyzer (AA) quantitation and chemiluminescence l£st (CLT) performed on maternal anti-D serum during pregnancy to discriminal£ babies affected or unaffected by HDN has been studied. It was found that all methods had their weaknesses, but AA-quantitation and CLT improved speeifieity when compared to the IAT-titration method. However, a great improvement was achieved when the results of IAT-titration and AA-quantitation, as determined by the cut-offlimits applied to discriminate unaffected from affected newborns, were combined; specificity was then found to increase from 60-78% to 93% and was further increased with the addition of the CLT test to 95%. Finally, the detection of HLA class II monocyte-reactive antibodies and their potential protective role in ameliorating HDN has been viewed.

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