652 - Utility of Transcutaneous Bilirubin Measurement in Predicting Early Need for Phototherapy in Newborns with Positive Direct Antiglobulin Testing

Publication Number: 1629.652

Timothy Porter, Brigham and Women's Hospital, Arlington, MA, United States; Hailey M. Foster, Brigham and Women's Hospital, Clearwater, FL, United States; Amanda C. Rivera-Morales, Brigham and Women's Hospital, Guaynabo, PR, N/A, Puerto Rico; Sara Cherkerzian, Brigham and Women's Hospital, Boston, MA, United States; Kathryn Dee MacMillan, Children's Hospital at Dartmouth-Hitchcock, Lebanon, NH, United States

Background: Neonatal hyperbilirubinemia is usually benign and self-limited; however, newborns with hemolysis are at higher risk for acute and chronic neurotoxicity. Direct antiglobulin (DAT) testing is frequently used to identify these patients, but it has limited diagnostic accuracy. A recent study found an early transcutaneous bilirubin (TcB) measurement was highly predictive of the need for phototherapy in ABO incompatible DAT positive newborns using the 2004 American Academy of Pediatrics (AAP) guidelines, but a similar approach has not been evaluated using the updated 2022 guidelines.

Objective: Determine the accuracy of a "Delta TcB" measurement (distance of TcB measurement below phototherapy threshold) in the first 12 hours of life (HOL) to identify newborns who received phototherapy during the birth hospitalization among a sample of newborns >=35 weeks gestational age (GA) at birth.

Design/Methods: A retrospective chart review was performed at a single center from 8/1/2022 through 7/31/2025. Clinical and demographic data were recorded and analyzed for Receiver Operator Characteristic (ROC) Curve analyses, assessing for area under the curve (AUC) and predictive values at optimal threshold. Subgroup analyses using AUC differences were performed for infant sex, infant blood type, maternal race, and maternal ethnicity (as proxies for infant race and ethnicity).

Results: Among 20,191 qualifying births, 439 (2.2%) newborns were DAT positive, and of those, 231 had a TcB value measured within the first 12 HOL. 51 of these newborns received phototherapy during the birth hospitalization, including 24 in the first 24 HOL (Table 1). Early Delta TcB was highly predictive of receiving phototherapy in the first 24 HOL (negative predictive value (NPV) 0.98, AUC 0.96 (95% Confidence Interval (CI) 0.94-0.99) at an optimal threshold of 2.65 mg/dL (Figure 1). Early Delta TcB was also predictive of receiving phototherapy at any age during the birth hospitalization (NPV 0.93, AUC 0.86 (95% CI 0.8-0.92) at an optimal threshold of 3.55 mg/dL. No significant differences were observed among subgroups for the AUC predicting need for phototherapy in the first 24 hours of life (Figure 2).

Conclusion(s): Early measurement of Delta TcB in the first 12 hours of life demonstrated strong negative predictive value for DAT positive infants >= 35 weeks GA at birth receiving phototherapy during the birth hospitalization, especially in the first 24 hours of life. This may be a reasonable approach to identify infants at lower risk for clinically significant hemolysis and to decrease need for frequent testing and associated costs.

Characteristics of DAT Positive Newborns According to Phototherapy Status
Differences by phototherapy status were tested using Wilcoxon Rank Sum test for continuous measures and chi square test (Fisher's exact where cell size < 5) for categorical. DAT, direct antiglobulin test; SD, standard deviation; IQR, Interquartile Range.

Receiver Operator Characteristic (ROC) Curve Classification of Receiving Phototherapy Using the Delta TcB
A) Phototherapy in the first 24 hours of life; B) Phototherapy at any age during birth hospitalization. Delta TcB = phototherapy threshold minus TcB value in mg/dL. ROC, receiver operator characteristic.

ROC Curve Subgroup Analyses
Classification of Receiving Phototherapy in the first 24 HOL by A) Infant Sex; B) Maternal Race; C) Maternal Ethnicity; D) Infant Blood Type. ROC, receiver operator characteristic.