N REBOUND JAUNDICE NN

Two variables, gestational age at phototherapy initiation and the difference between starting threshold and post-phototherapy total serum bilirubin (TSB), accurately predict rebound hyperbilirubinemia in infants, researchers report.

This can help clinicians decide when it's safe to discontinue phototherapy for infants undergoing treatment of neonatal jaundice, note Dr. Pearl W. Chang from Seattle Children's Hospital and Dr. Thomas B. Newman from the University of California, San Francisco, and Kaiser Permanente Northern California, in Oakland.

The two previously devised a three-variable clinical prediction rule that quantified the rebound risk after the first inpatient phototherapy. In the current study, they sought to determine if a two-variable model would perform as well.

Among the 7,048 infants included in the study, all of whom underwent their first inpatient phototherapy before age 14 days, the mean difference between the starting threshold and the ending TSB was 4.4 mg/dL. Overall, 4.6% developed hyperbilirubinemia.

The equation for the score derived from these infants is calculated as 15.5 (if gestational age is <38 weeks) minus (4.3 times (starting threshold minus ending TSB)).

The score had a similar accuracy (AUROC, 0.877) as the three-variable model (0.887), which relied on gestational age (GA), age at phototherapy initiation, and TSB relative to the American Academy of Pediatrics phototherapy threshold.

The researchers translated the score into a predicted probability of rebound hyperbilirubinemia: 1/(1 + exp(-(0.097 * score - 2.84)), which can be readily programmed into a spreadsheet or other application.

"Stopping phototherapy at 2 mg/dL below the starting threshold gave a rebound probability of 2.5% for infants at or beyond 38 weeks' gestation and 10.2% for infants <38 weeks' gestation," they write in Pediatrics, online June 13. "For infants <38 weeks' gestation, phototherapy would need to be stopped at 5.5 mg/dL below the starting threshold to have a rebound probability (2.6%) similar to that of infants at or beyond 38 weeks' GA who stopped phototherapy at 2 mg/dL below the starting threshold."