Transcutaneous Bilirubin Measurements in Preterm Infants: The Impact of Race, Age, and Phototherapy

Background Monitoring bilirubin in preterm neonates is essential to prevent neurotoxicity. Total serum bilirubin (TSB) remains the diagnostic standard, while transcutaneous bilirubinometry (TcB) offers a rapid, non-invasive, and cost-effective alternative. However, TcB’s accuracy in preterm infants, especially during phototherapy and across racial or gestational groups, remains uncertain. Objective To assess concordance between TcB and TSB in preterm neonates across gestational ages, racial/ethnic groups, and phototherapy exposure. Methods We analyzed 330 paired TcB-TSB readings from 113 preterm infants (postnatal age 5–408 hours, mean ± SD: 91.8 ± 64.2) in a NICU. Infants were categorized by gestational age (< 28, 28–32, 32–36 weeks) and by self-reported maternal race and ethnicity. We employed correlation analysis, paired t-tests, linear regression, and Bland-Altman plots. TcB was evaluated under phototherapy (exposed vs. patched skin) in relation to escalation of care thresholds (ECT). Results TcB and TSB were strongly correlated overall (r = 0.822), but the level of agreement varied by gestational age and phototherapy exposure. Accuracy declined with phototherapy, especially on exposed skin. Bland-Altman analysis showed that TSB and TcB are not interchangeable. Finally, TcB-ECT concordance was low. Conclusion TcB correlates with TSB but lacks sufficient accuracy for standalone use in preterm infants, particularly during phototherapy. Caution is called for in clinical application.