Utility of DAT in Low-Risk Neonates with ABO or RhD Incompatibility

BACKGROUND: Routine direct antiglobulin test (DAT) screening in newborns at risk of isoimmune hemolytic disease is a long-standing practice. Advancements in prophylactic care and noninvasive hyperbilirubinemia monitoring warrant reevaluating the value of DAT. We investigated the clinical utility of routine DAT screening for mature newborns with ABO incompatibility and ABO-compatible newborns with RhD incompatibility born to mothers without active alloimmunization. METHODS: We conducted a retrospective cohort study of infants born after 35 weeks or more of gestation undergoing DAT screening. Infants were stratified into ABO-incompatible and ABO-compatible/RhD-incompatible cohorts. Bivariable correlations, logistic regression, and area under the receiver operating characteristic curve (AUC) were used to assess predictors for phototherapy requirements. RESULTS: Among 618 infants included in the analysis, within the ABO-incompatible cohort (N = 310), DAT positivity was associated with higher transcutaneous bilirubin (TcB) and increased phototherapy requirement. However, TcB alone robustly predicted the phototherapy requirement (AUC = 0.887). Incorporating DAT minimally enhanced the predictive capacity (AUC = 0.896). In the ABO-compatible/RhD-incompatible cohort (N = 308), 14.0% of infants had a positive DAT attributed to passive maternal anti-D, showing no correlation with TcB. Only 1.0% of these infants required phototherapy. CONCLUSIONS: Our data showed routine DAT screening provides minimal predictive value beyond TcB monitoring for ABO-incompatible infants and offers no clinical utility for RhD-incompatible infants exposed solely to passive anti-D. These findings validate the 2022 American Academy of Pediatrics guidelines, suggesting that discontinuing routine DAT in these low-risk populations safely optimizes laboratory resources. Importantly, maternal antibody screening remains essential, and DAT must be performed if maternal screening is incomplete or unavailable.