Sixth-Hour Trancutaneous Bilirubin and Need for Phototherapy in DAT Positive Newborns.

OBJECTIVES

To characterize the outcomes of ABO incompatible direct antiglobulin test (DAT) positive newborns and determine the predictive ability of a sixth-hour transcutaneous bilirubin (TcB for needing phototherapy ≤24 hours of age.

METHODS

Retrospective, cross-sectional study from May 2013 to March 2017. Of 10 942 consecutive newborns ≥35 weeks estimated gestational age, 829 were ABO incompatible and DAT positive. After excluding for antibodies other than ABO (51), missing data (4), miscategorization of blood type O (1), and duplicate record (1), 772 newborns remained. Of 772, a subsample of 346 newborns with both TcB and total serum bilirubin (TSB) tests within 1 hour of the sixth hour was analyzed to determine the predictive ability.

RESULTS

Phototherapy was required in 281 of 772 (36.4%); 156 (20.2%) in the first 24 hours. There were 10 (1.3%) admissions for hyperbilirubinemia to the NICU for intravenous immunoglobin. Birth weight, infant blood type B, TSB, reticulocyte count, and TcB were all significantly associated with phototherapy ≤24 hours. On multivariate analysis, significant predictors of phototherapy ≤24 hours were TSB and reticulocyte count if no TcB was done and TcB alone if no blood tests were done. TcB was highly predictive (odds ratio 3.1, 95% confidence interval: 2.4-4.0) and nearly as accurate as the TSB and reticulocyte count (area under the curve, 0.90 and 0.96, respectively). Low (<3.0 mg/dL) and high (≥5.3 mg/dL) risk TcB cutoffs demonstrated a negative predictive value of 98% and positive predictive value of 85%, respectively.

CONCLUSIONS

Among high-risk ABO incompatible DAT positive newborns, the sixth-hour TcB is highly predictive of the need for phototherapy ≤24 hours.