Background UK guidelines advocate the use of transcutaneous bilirubin (TCBR) estimation in neonates with jaundice aged >24 h with a gestational age of ≥35 weeks, but not in neonates who have had phototherapy, as there is a more rapid fall in dermal vs. serum bilirubin with phototherapy. A recent study demonstrated that whilst TCBR underestimated SBR within the first 8 h after phototherapy, its accuracy returned to pre-treatment values after 24 h. This suggests a possible role for TCBR monitoring in infants who have had phototherapy >24 h ago, reducing the number of both blood tests and hospital visits.

Aim To compare TBCR and SBR measurements before, during and after phototherapy in neonates.

Methods This was a prospective observational study at a UK district general hospital. Participants were all neonates admitted to the neonatal unit or postnatal ward who required an SBR measurement for jaundice monitoring as per UK guidelines. TBCR measurement was performed using a Dräger Jaundice Metre JM-103 within 10 min of the SBR sampling. SBR was determined by blood gas analysis. Safety margins (mean difference – 2.33 × SD – 50) were calculated for TCBR readings during phototherapy to correctly assign 99% of neonates to stop receiving phototherapy, i.e. SBR >50 μmol/l below the treatment threshold.

Results Pilot data: 8 neonates (gestation 34 + 4 to 42 + 0, 4 male) had a total of 11 simultaneous measurements. Measuring TCBR on the forehead, the mean (SD) difference (TCBR - SBR) before phototherapy was -45 μmol/l (17 μmol/l), during phototherapy was −102 μmol/l (8 μmol/l), and at >16 h after phototherapy was −48 μmol/l (6 μmol/l). Values were similar measuring TCBR on the sternum. During phototherapy, TCBR levels of −171 μmol/l below the treatment threshold allowed safe cessation of phototherapy without confirmatory SBR testing.

Conclusion TCBR measurements >16 h after phototherapy appear to be equally as accurate as before phototherapy, which could obviate the need for SBR measurement when checking for a rebound rise in bilirubin after stopping phototherapy. More comprehensive data will be collected in time for presentation at the RCPCH Conference.