Abstract: Objective The study aimed to investigate the relationship between the results of the three hemolysis tests,age on admission,and total serum bilirubin（TSB） in ABO hemolytic disease of the newborn(HDN). Methods Four hundred and eleven cases with ABO HDN admitted to the Affiliated Hospital of Qingdao University between December 2016 and April 2020 were selected. The three hemolysis tests and TSB were tested. We did a retrospective analysis of their clinical data,such as age on admission. Results Among the 411 infants,admission age,positive or negative direct antiglobulin test（DAT）, and positive or negative results for the three hemolysis tests were statistically significant differences（P<0.05） in TSB levels,except for gestational age and birth weight. The rates of positive DAT newborns were 50%,46.67% and 3.33% in admission age groups of ≤1 d,2~4 d and ≥5 d,respectively. The difference was statistically significant（P<0.05）. Excluding cases with gestational age less than 35 weeks and birth weight less than 2 500 g,the correlation coefficient between TSB levels and age on admission was 0.42（P<0.001）. The median TSB levels were 176.37 μmol/L,220.20 μmol/L,and 271.10 μmol/L in age on admission group of ≤1 d, 2~4 d and ≥5 d,respectively. After we applied Bonferroni corrections,the difference was statistically significant（P<0.001）. The older the age on admission,the higher TSB levels in newborns the lower the DAT positive rate. Conclusion For newborns with suspected ABO HDN,the three hemolysis tests are performed in time. Earlier diagnosis and intervention reduce the occurrence of major adverse events.

Key words: ABO incompatibility, Haemolytic disease of the newborn, Hyperbilirubinemia