Can transcutaneous bilirubinometry safely be used to monitor rebound hyperbilirubinaemia after phototherapy in neonates ≥35 weeks' gestation? A prospective, comparative study.

Introduction: There is insufficient evidence to determine if non-invasive transcutaneous bilirubin (TcB) measurement can replace serum bilirubin (SBR) in assessing rebound hyperbilirubinaemia after phototherapy.

Objective: To investigate if TcB can safely guide management of neonates after phototherapy.

Subjects: 100 well neonates ≥35 weeks' gestation who had received inpatient phototherapy.

Method: Measurement of both helix (manufacturer's recommendation) and earlobe TcB coincidentally with routine SBR 12 hours after cessation of phototherapy. All mothers gave written informed consent.

Results: Gestation ranged from 35 to 41 (median 37) weeks; birth weight 2018-4566 (median 3230) g; age 55-222 (median 109) hours at testing. 86% neonates were Caucasian. Outcomes determined by SBR included restarting phototherapy (n=0), repeat SBR next day (n=29), no further routine follow-up (n=71).TcB and SBR measurements were unpredictably inconsistent. Helix TcB tended to underestimate SBR (mean difference 50.1 (95% CI 113.9 to -13.7) μmols/L); for earlobe TcB mean difference was -13.4 (95% CI 46.3 to -73.2) μmols/L (overestimate), but bias was greater over the range of mean differences. No demographic factor predicted consistency between TcB and SBR. TcB was 25% (helix) and 76% (earlobe) sensitive in predicting repeat phototherapy and/or repeat SBR; specificities were 92% and 58%, respectively. Adding a safety margin of 120 μmols/L to helix TcB value could have safely avoided invasive SBR measurement in 50/98 (51%) babies.

Conclusions: Consistency between TcB and rebound SBR is unpredictable in well neonates 35 weeks' gestation but adopting a wide safety margin has potential to reduce blood sampling. Recommencement of phototherapy is uncommon in this population.