Predicting the severity of haemolytic disease of the newborn: an assessment of the clinical usefulness of the chemiluminescence test.

The ability of the chemiluminescence test (CLT) to predict the severity of haemolytic disease of the newborn (HDN) was determined in 80 alloimmunized pregnant women who delivered antigen-positive babies. In 54 cases of alloimmunization to D, results from the CLT showed better correlation with fetal outcome than anti-D concentration measured by AutoAnalyzer (r = 0.70 and 0.36 respectively). Results from the CLT permitted a threshold level of antibody activity (30%) below which 15/20 babies were unaffected or had mild disease, and only one required transfusion therapy in utero. CLT results above 30% were associated with moderate or severe disease in all cases. Results from the AutoAnalyzer proved a less reliable predictor of disease severity; three women with anti-D levels > 20 iu/ml delivered unaffected babies, and two women with anti-D levels < 10 iu/ml delivered babies who had required transfusion in utero. The clinical usefulness of the CLT derives from the possibility of avoiding invasive monitoring procedures in women with high levels of anti-D which is relatively non-functional.