LAUSR

Objective To examine the accuracy of transcutaneous bilirubinometry (TCB) measurements during and after phototherapy (PT) in preterm infants. Design Prospective observational cohort study. Setting Level III neonatal centre. Patients Preterm infants (from 23+0 to 36+6 weeks of gestation) born between June 2017 and May 2018 requiring PT. Interventions TCB was measured from an exposed area of the skin (the sternum; TCBU) and the covered area of the skin under the nappy (the bony part of the upper outer quadrant of the buttock; TCBC) within an hour of obtaining total serum bilirubin (TSB). Main outcome measures Correlation and agreement between TCB (TCBU and TCBC) and TSB during and after PT. Results We have enrolled 196 preterm infants. There was a significant correlation between TSB and TCB during PT (r=0.72, 95% CI 0.66 to 0.77 in covered area; r=0.75, 95% CI 0.70 to 0.80 in uncovered area) and after PT (r=0.87, 95% CI 0.83 to 0.91). TCB underestimated TSB level during PT, with a mean TCBC–TSB difference of −25±43 (95% agreement limits of 62 to −112) and a mean TCBU–TSB difference of −48±46 (95% agreement limits of 45 to −140). The agreement between TCB and TSB after cessation of PT improved, with TCB underestimating TSB by a mean TCB–TSB difference of −10±31 (95% agreement limits of 52 to −72). Conclusion TCB measurements correlated strongly with TSB levels during and after PT. However, there was a wide and clinically relevant disagreement between TCB and TSB measurements during the PT phase, improving significantly after PT.