A Retrospective Study of Red Cell Maternal Antibodies by Chemiluminescence

Plasma samples from 109 patients with maternal IgG alloantibodies were investigated using a chemiluminescence (CL) assay, a functional test, to predict which antibodies were clinically significant. The CL assay was able to distinguish between those patients who were unaffected or mildly affected requiring only phototherapy, and those patients with moderate or severe haemolytic disease of the fetus or newborn (HDN) requiring transfusion therapy. The CL result was compared with the anti-D quantification result, the number of IgG molecules bound per red cell and, in 80% of the cases, the monocyte monolayer assay. If mothers carrying Rh-negative fetuses were ignored, then the CL assay correctly predicted the outcome for 93.4% of all cases (including those other than D), while the AutoAnalyzer and monocyte assay predicted correctly 92.7% (of the anti-D patients) and 81.5%, respectively. Greater than 80% of patients with severe or moderate HDN had both IgG1+IgG3 subclasses in the maternal plasma, while those infants who were unaffected or only mildly affected had a greater chance of having IgG1 only (44%) in the maternal plasma, IgG3 only (27%) or both subclasses (29%).