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Investigators from Naval Medical Center Portsmouth (NMCP), Portsmouth, VA, and the University of Pittsburgh School of Medicine, Pittsburgh, PA, conducted a retrospective study to assess the utility of a transcutaneous bilirubin (TcB) measurement at 6 hours of age in predicting the need for phototherapy at ≤24 hours of age in newborns with ABO incompatibility. Data on neonates born at NMCP between May 2013 and March 2017 who were ≥35 weeks’ gestation were reviewed. Infants were classified as having ABO incompatibility if born to mothers with type O blood and negative antibody screens and themselves had type A or B blood with positive direct antiglobulin tests (DAT).
At NMCP, blood is obtained from newborns with ABO incompatibility at 6 hours of age for total serum bilirubin (TSB), hemoglobin, hematocrit, and reticulocyte counts; providers are encouraged to also obtain a TcB measurement. Infants with paired blood test and TcB results were included in study analyses; demographic and clinical data were abstracted from the medical records of these newborns. The primary study outcome was need for phototherapy at ≤24 hours of age, as determined by the attending pediatrician. Demographic and clinical characteristics associated with this outcome in univariate analyses were included in 2 logistic models; 1 with blood test results and no TcB levels, and the other with TcB results and no blood test data. Receiver operator characteristic (ROC) curves were constructed and the area under the curve (AUC) calculated. The positive and negative predictive values (PPV and NPV, respectively) of different TcB cutoff values in predicting the need for phototherapy at ≤24 hours also were determined.
Among 10,942 newborns born at ≥35 weeks’ gestation, 5,167 (47.2%) were born to mothers with type O blood, DAT was positive in 829 (7.6%), and 772 (7.1%) infants met criteria for ABO incompatibility. A total of 346 newborns had paired blood test and TcB results, 21% of whom were treated with phototherapy at ≤24 hours of age. In univariate analyses, birth weight, type B blood, TSB level, reticulocyte count, and TcB were significantly associated with the need for phototherapy at ≤24 hours. In the multivariate model that excluded TcB results, only TSB and reticulocyte counts were independently associated with the outcome (odds ratio [OR], 12.6; 95% CI, 6.1, 25.6; and OR, 1.5; 95% CI, 1.0, 2.1, respectively). In the other model, TcB was significantly associated with the need for phototherapy at ≤24 hours of age (OR, 3.1; 95% CI, 2.4, 4.0). The ROC AUCs were similar for the 2 models (0.96 and 0.90, respectively). A TcB value of ≤3.0 mg/dL yielded a NPV of 98%, a value of ≥5.3 mg/dL, and a PPV of 85% for predicting the need for phototherapy at ≤24 hours of age.
The authors conclude that a 6-hour TcB level was predictive of the need...
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