Auto Analyzer quantification, monocyte‐mediated cytotoxicity and chemiluminescence assays for predicting the severity of haemolytic disease of the newborn

Abstract

Summary. The value of quantitative and functional assays in predicting the severity of haemolytic disease of the newborn (HDN) was assessed. Sera containing anti‐D were obtained from 27 pregnant women who subsequently delivered D‐positive babies. Antibody levels were quantified by Auto Analyzer (AA) and functional activity was determined by an antibody‐dependent cell‐mediated cytotoxicity (ADCC) and chemiluminescence test (CLT). The severity of haemolytic disease was graded according to cord Hb levels and transfusion requirements of the babies. In eight cases unaffected by HDN, six results by AA (over 5IU/ml), one by CLT and two by ADCC falsely predicted the occurrence of HDN. In nine cases of mild to moderate HDN requiring transfusion therapy, there was one false negative result by AA, three by CLT and two by ADCC. All assays correctly predicted severe HDN in the remaining 10 cases. The ADCC assay and CLT showed good correlation (t= 0·69, P < 0·001) and the tests were of comparable sensitivity. The data suggest that while all assays are capable of discriminating severe HDN, AA results may falsely predict HDN in unaffected babies. Although the CLT may not discriminate some mild cases of HDN, ADCC and CL tests are less susceptible to false positive results in unaffected cases.