Can transcutaneous bilirubin levels obtained from covered skin replace serum bilirubin measurement in neonates undergoing phototherapy?

Background: Transcutaneous bilirubinometers provide a non-invasive method to estimate total serum bilirubin (TSB) using multiwavelength reflectance. However, their accuracy during phototherapy (PT) remains controversial due to decreased dermal bilirubin. Objective: To assess the correlation between TSB and transcutaneous bilirubin (TcB) measured from covered and exposed skin areas before, during, and after PT. Methods: In this prospective study, 70 neonates undergoing PT were assessed. TcB measurements were obtained from the exposed sternum and the forehead, which were covered with an aluminum-coated radiopaque patch. TSB and TcB values were measured before PT, at 24 h during treatment, and 8 h post-treatment. The agreement between TSB and TcB values was evaluated using the intraclass correlation coefficient (ICC). Results: TcB values of covered skin showed significant correlation with TSB at all-time points (ICC = 0.665 for pre-PT, ICC = 0.520 at 24 h, and ICC = 0.537 for post-treatment). TcB values of exposed skin showed poor correlation during and after PT. Mean differences between covered TcB and TSB remained within acceptable limits (<1 mg/dL). Conclusion: TcB measurements from covered skin offer a reliable, non-invasive alternative to serum bilirubin levels in neonates receiving PT, reducing the need for repeated blood draws.