The prevalence of ABO-HDN
We carried out screening on 7 513 mothers and 7 810 newborns between November 2016 and April 2020. Hospitalization information was collated from all neonates diagnosed with ”ABO haemolytic disease of the newborn” (including ”ABO haemolytic jaundice” and/or ”ABO haemolytic anaemia”), including maternal blood group, gestation at delivery, mode of delivery, the infant’s sex and birth weight, date of birth, time of admission, blood type, direct anti-globulin test (DAT), indirect anti-globulin test (IAT), eluate test, peak total serum bilirubin (TSB, μmol/L), haemoglobin (Hb, g/L), and treatment measures. All maternal blood groups, including Rh and irregular antibody screens, were tested at least once during pregnancy.
Neonates were assessed for blood type and subjected to DAT, IAT, and the eluate test if the newborn ABO was incompatible with that of the mother and the newborn developed neonatal jaundice simultaneously. Once the eluate test was positive and clinically significant jaundice occurred, infants were continuously monitored in an inpatient setting, whereas those who did not develop clinically significant jaundice were evaluated as outpatients. TSB and Hb were tested anytime when visual assessment and transcutaneous bilirubin were abnormal during hospitalization. ”ABO haemolytic jaundice” was defined when the eluate test was positive and the infant developed clinically significant jaundice, which was judged as any single total bilirubin result above the newborn infant 35 or more weeks of gestation phototherapy treatment threshold on charts from the American Academy of Paediatrics on Neonatal Jaundice [15]. ”ABO haemolytic anaemia” was defined as eluate test positive and Hb ≤ 145 g/L.
DAT and IAT tests were performed routinely at the blood bank of the Affiliated Hospital of Qingdao University on umbilical cord blood with an agglutination technique. The eluate test was performed by the heat dispersion method to remove RBC-bound antibodies. EDTA-anti-coagulated peripheral whole blood was centrifuged at 1 760 ×g for 5 min, drawing at least 2 ml of erythrocytes with a pipette tip for testing. After six washes of erythrocytes with 0.9% normal saline, the last release solution was used as the negative control. An equal volume of saline was added, and samples were incubated with shaking in a 56°C water bath for ten minutes. Samples were next centrifuged at 1 000 ×g for three minutes, immediately followed by transferring the supernatant red emission solution to the other three test tubes. One drop of A, B, and O RBC reagent (Changchun Boxun Biotechnology, Changchun, China) was added to the test tube, after which the samples were centrifuged and observed. Agglutination indicated that the RBC was attached to the corresponding antibodies and the eluate test was regarded as positive.