Quantitative and functional assessment of anti-RhD: A comparative study of non-invasive methods in antenatal prediction of Rh hemolytic disease

Study objective. To investigate if the prediction of hemolytic disease of the newborn (HDN) in infants of RhD immunized women has been improved by introduction of AutoAnalyzer quantitation and may be further improved by the use of a functional assay. Methods. Manual antibody titration. AutoAnalyzer quantitation and chemiluminescence test (CLT) were compared by testing 42 sera from 38 RhD immunized mothers, The sera were also screened for the presence of monocyte-reactive antibodies which have the potential to protect the unborn. Results. Among the 42 infants there were 19 unaffected by HDN and 23 affected by HDN. Manual titration correctly predicted the occurrence of HDN in 29/42 (69%). AutoAnalyzer was correct in 28/42 (67%) and CLT showed correct predictions with 30/42 (71%). In babies born without signs of HDN. maternal monocyte-reactive antibodies were found in 13/18 cases. The majority (9/13) were HLA class I-specific, the remaining four antibodies were either HLA class II or monocyte-specific. In affected HDN group, 8/16 monocyte-reactive antibodies were HLA class Ii or monocyte-specific. Conclusions. AutoAnalyzer and CLT improve the ability to discriminate unaffected babies from those affected by RhD HDN. when compared to manual titration. A protocol for the laboratory management of RhD immunized women is proposed that includes these tests to further improve the prediction of HDN. This study has also highlighted the need for more investigations into the protective role of monocyte-reactive antibodies in HDN.