Author Response

The authors thank Dr Manzar for the interest in and comments about our study, which raise several points worthy of further discussion.

Although the phototherapy nomogram (American Academy of Pediatrics hyperbilirubinemia guideline, Fig 3)¹  does provide riskstratified treatment thresholds at the sixth hour, there is a notation that “these guidelines are based on limited evidence and the levels shown are approximations.” The studies that contributed to these approximations primarily focused on identifying high-risk newborns before discharge, with bilirubin measurements most often after 24 hours. The well-known study that generated the Bhutani nomogram excluded newborns who were direct antiglobulin test (DAT) positive and only reported on total serum bilirubin measurements (TSB), not transcutaneous bilirubin (TcB).²  The average TSB in this study was 34 hours with few measurements <18 hours and no TSB measurements <12 hours. Therefore, the reliability of the approximations in Fig 3¹  is lower in the first 18 hours after birth.

As summarized in our discussion section,³  there are very few studies that have assessed sixth-hour bilirubin measurements, even fewer with TcB measurements, and none that have done so in a large population of highrisk ABO incompatible, DAT-positive newborns. Our study provides important new data for a different test (TcB rather than TSB) derived from a different population than depicted in Fig 3.¹  As Dr Manzar points out, the high-risk threshold of ≥5.3 mg/dL that we determined was similar to the estimate in Fig 3,¹  depending on gestational age, which was not an independent predictor of phototherapy in our study.

As we discussed in our paper, a significant proportion of newborns with ABO incompatibility who are DAT-positive require phototherapy in the first 24 hours, and it would be beneficial to identify them and start treatment earlier, something the AAP guideline does not ideally address. It is our hope that our data may augment the AAP guidelines by providing reassurance that an early sixth-hour TcB provides a reliable prediction of the risk of phototherapy not only for ABO incompatible, DATpositive newborns, but for any newborn because babies who develop severe hyperbilirubinemia often have >1 cause. The TcB is inexpensive and can reliably limit the number of atrisk newborns needing a TSB, especially at newborn nurseries that are routinely doing cord blood testing of babies of blood type O mothers.

Because we only recently analyzed and published our data, we are evaluating and assessing the feasibility of incorporating a routine sixth-hour TcB at our own institutions; therefore, we do not yet have implementation data addressing any potential practice change.

AAP

American Academy of Pediatrics

PTX

phototherapy

TcB

transcutaneous bilirubin