Routine direct antiglobulin testDirect antiglobulin test A blood test used to detect antibodies attached to red blood cells. It helps confirm HDFN in newborns. (DATDirect antiglobulin test A blood test used to detect antibodies attached to red blood cells. It helps confirm HDFN in newborns.) screening appears to add little clinical value for most newborns at risk for hemolytic disease of the fetus and newborn (HDFN), particularly when modern bilirubinBilirubin A yellow substance produced when red blood cells break down. High bilirubin levels in newborns with HDFN can cause jaundice or, in severe cases, brain damage. monitoring is available, according to a study published recently in Pediatrics.
A retrospective cohort study found that transcutaneous bilirubin measurements, which is a noninvasive way to estimate a newborn’s bilirubin level by gently measuring the skin, were nearly as effective as transcutaneous bilirubin plus DAT in predicting which ABO-incompatible infants would need phototherapyPhototherapy A treatment that uses special blue light to help newborns break down bilirubin and prevent kernicterus.. These findings support the 2022 American Academy of Pediatrics guidelines and could reduce unnecessary testing for newborns and hospitals.
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“Consequently, routine DAT in these populations may be unnecessary, and transitioning to a targeted testing approach could optimize neonatal care and laboratory resources,” explained the study’s authors. They continued, “However, it is essential to emphasize that the safety of this targeted approach relies heavily on the completion of maternal antibodyAntibody A protein made by the immune system that recognizes and attacks foreign substances, such as bacteria, or in HDFN, fetal red blood cells carrying incompatible antigens. screening.”
This analysis included 618 infants born at 35 weeks or more of gestation. Of these, 310 had ABO incompatibility and 308 had ABO-compatible/RhD-incompatible blood types. Among ABO-incompatible infants, a positive DAT was associated with higher transcutaneous bilirubin levels and greater phototherapy requirements.
However, transcutaneous bilirubin alone was highly accurate at predicting which infants would need phototherapy, with an area under the curve of 0.887 (95% CI, 0.839–0.936), meaning it was able to distinguish very well between babies who did and did not need treatment. Adding DAT increased the area under the curve only slightly, to 0.896 (95% CI, 0.848–0.944), showing that the additional test provided little improvement in identifying which babies would need phototherapy.
For families, this means that a newborn who has an ABO blood-type mismatch with the mother may not need a routine DAT simply because of that mismatch. Instead, clinicians can monitor bilirubin levels, which can help identify babies developing jaundiceJaundice A common symptom of HDFN, jaundice is caused by excess bilirubin and is characterized by a yellow tint to the skin or eyes. that could require treatment. This study’s findings were particularly notable because the hospital used targeted DAT testing in some infants based on clinical concerns, meaning the ABO-incompatible group may have had a higher baseline risk than a universally screened population.
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The results were even more reassuring for newborns with ABO-compatible but RhD-incompatible blood types. Among these 308 infants, 196 mothers (63.6%) had positive prenatal antibody screens caused exclusively by passive anti-D from RhRh factor A protein or antigen found on red blood cells. When an Rh-negative mother carries an Rh-positive fetus, her immune system may make antibodies that attack the fetus' red blood cells. immune globulin. Forty-three newborns (14.0%) had positive DAT results, likely because of passive anti-D exposure. Only 3 infants (1.0%) ultimately required phototherapy, and DAT results did not correlate with TcB levels.
These findings suggest that passive anti-D from standard Rh immune globulin prophylaxis does not appear to create a meaningful hemolysis risk in this population. For patients and families, the potential benefit is less blood testing and more focused monitoring without reducing vigilance for clinically important HDFN. Maternal antibody screening remains essential, however, and DAT testing should still be performed when maternal screening is incomplete or unavailable.
The study’s authors suggest reserving DAT for newborns who develop clinically significant hyperbilirubinemiaHyperbilirubinemia A common cause of jaundice, this refers to higher than normal bilirubin levels in the blood., when the result can help determine HDFN-related risk and treatment thresholds. For families, this approach shifts testing from routine screening toward individualized care, while maintaining bilirubin surveillance and preserving DAT as an important diagnostic tool when jaundice or other concerns arise.
