The great variation of the distribution of ABO and RhD blood groups has led to distinct distribution of types of HDN throughout the world. A, O and RhD + were the most frequent phenotypes in ABO and RhD blood groups respectively in mainland China. In 2012, Guo N’s study18 enrolled 512594 donations at five blood centers in China reported that O phenotype was the most frequent (34.0%) and RhD– phenotype was 1.0%, in 2017, Liu J’s research showed that blood group A (30.4%) and O (30.2%)
appeared to be the most common phenotype and RhD– phenotype was 0.95% among 3473527 Han ethnicity from China19. However, the proportion of RhD– phenotype has
been reported to be 14.6% in the USA20, 17.9% in Sweden and Denmark21, therefore, in mainland China, researches on HDN mainly focus on ABO-HDN rather than Rh-HDN compared with HDN studies on Caucasian populations. Meanwhile, East Asian race with ABO-HDN has higher risk of severe hyperbilirubinemia22 which may lead to acute and chronic nervous system damage with no early intervention. In severe ABO-HDN cases, transfusions of blood components were required usually to reduce jaundice, prevent and treat anemia, however, blood components transfusion may lead to transfusion transmitted diseases, anaphylaxis, hypersensitivity, thrombosis, electrolyte disturbance and renal failure as well as high hospitalization cost.
The incidence of positive DAT in ABO-HDN ranges greatly due to the different DAT techniques and population examined, in this study, the incidence of positive DAT is 25.6% (69/270), previously, Valsami S et al retrospectively reviewed routinely performed DAT of all infants born between January 2011 and December 2012 in Greece showed that, among 481 ABO incompatible infants, 64 cases are confirmed as DAT positive (positive rate is 13.3%)23 and a 2-year retrospective study with a large sample size of ABO-incompatible neonates of black ethnicity showed that 270 of 1537 cases are DAT positive with the positive rate of 17.6%24 The incidence of positive DAT is higher than that of previous reports, in addition to race differences, that DAT was used as screening test to perform in all cases with suspected ABO-HDN instead of infants with confirmed ABO-HDN in our study, could be the main reason cause of this difference, hence, even if the positive rate of DAT has risen with the increase of the possibility of ABO-HDN in the study population, the incidence of positive DAT in ABO-HDN is still low, illustrating DAT a poor positive predictor of ABO-HDN. Moreover, we investigated the clinical value of DAT in severe hyperbilirubinemia in the present study, although ABO-HDN refers to be the major reason of positive DAT, whether DAT could be a prediction factor for severe hyperbilirubinemia is still controversial, some studies reported that the positive DAT has only a poor predictive value for severe hyperbilirubinemia because of only approximate 23% cases of ABO-HDN with positive DAT will continue to have significant hyperbilirubinemia25,26, however, this study shows that DAT has a predictive value for the severe ABO-HDN hyperbilirubinemia with the DAT level cutoff value of ± has the highest sensitivity and specificity in terms of accurately predicting severe ABO-HDN hyperbilirubinemia, Mehta R’s study14 enrolled 901neonates with gestational age > 34 weeks and birth weight > 2000 g showed that the risk for hyperbilirubinemia requiring phototherapy in the DAT positive infants is significantly higher than that in the neonates with negative DAT (OR 6.78, 95% CI 2.38–19.33) and previous studies demonstrated that ABO-HDN with a positive DAT is considered a major risk factor for the development of severe hyperbilirubinemia and neurotoxicity27,28 as well.
The combination detection29 of DAT and detection factors including the blood cell indices, pre-discharge total bilirubin level, cord serum albumin and cord bilirubin/albumin ratio30 would be more beneficial than that of DAT alone for predicting the severity of ABO-HDN. Among them, cord serum albumin and cord bilirubin/albumin ratio have been well researched as the result of the mechanism of bilirubin metabolism in infants, in plasma, bilirubin binds to albumin to form the bilirubin albumin complex in order to transport to the liver for further metabolism, on one hand, bilirubin binding to albumin increases the water solubility of bilirubin and improves the plasma capacity of transporting bilirubin, on the other hand, it limits the free permeability of bilirubin to various cell membranes and avoids toxic effect of bilirubin on tissues and cells31,32, therefore, low serum albumin level decreases bilirubin clearance and thus increases significant hyperbilirubinemia, previous studies33,34 found that term infants cases with low cord albumin < 2.8 g/dl developed more significant hyperbilirubinemia requiring phototherapy and exchange transfusion and Khairy MA and colleagues33 showed that neonates with cord bilirubin/albumin ratio < 0.61 were at risk of developing significant hyperbilirubinemia needing interventions at the same time. However, both cord serum albumin level and cord bilirubin/albumin ratio are considered to reflect ability of albumin to bind bilirubin, AGR we assessed in the current study reflect the infant level of albumin remaining after binding bilirubin resulting in that high level of bilirubin may lead to decline of albumin level. Moreover, since this is the first analysis assessing the clinical value of AGR in severe ABO-HDN hyperbilirubinemia to the best of our knowledge, we plotted an ROC curve analysis and showed that AGR cutoff value < 2.05 had a good predictive value with a sensitivity of 54.1% and a specificity of 85.7%, meanwhile, we also demonstrated that combination detection of DAT and ARG had a better predictive value than that of respective detection of DAT and ARG in prediction of severe ABO-HDN hyperbilirubinemia (AUC for combination detection 0.750 VS AUC for DAT 0.621 and AUC for AGR 0.740). Finally, after dividing the infants into three groups according to the results of DAT and ARG and comparing phototherapy day and hospitalization day of the three groups, we found that group of AGR < 2.05 and DAT > ± had significant longer phototherapy day and hospitalization day than that of group of AGR < 2.05, group of DAT > ± respectively, prompting that the condition of infants with AGR < 2.05 and DAT > ± is more severe and meaning more hospital costs. With lack of studies done on ARG as a prediction factor of severe ABO-HDN hyperbilirubinemia, this work opens the window for further studies to be performed in this field and we are aware that larger scale trials including Multi ethnic researches and preterm neonates are needed.
To summarize, in this study DAT and AGR proved to predict the severity of ABO-HDN hyperbilirubinemia in term neonates. Infants with either DAT > ± or AGR < 2.05 were at risk of developing significant ABO-HDN hyperbilirubinemia. These can be considered possible predictors for severe ABO-HDN hyperbilirubinemia and combination detection of DAT and ARG can improve the predictive value. We recommend that pediatricians pay close attention to the results of DAT and AGR when judging the severity of ABO-HDN hyperbilirubinemia, particularly the term infants with DAT > ± and AGR < 2.05.