Comparison of Transcutaneous Bilirubin with Serum Bilirubin in Pre-Term Neonates Before, During, and After Phototherapy

Abstract

Objective: To assess the agreement between transcutaneous bilirubin (TcB) and total serum bilirubin (TSB) measurements before, during, and after phototherapy in preterm neonates with unconjugated hyperbilirubinemia.

Study Design: Prospective observational method-comparison study.

Place and Duration of Study: Neonatal Intensive Care Unit, Dr Sulaiman Al Habib Hospital, Al Rayyan, Riyadh, Saudi Arabia, from May to October 2024.

Methodology: A total of 199 preterm neonates with unconjugated hyperbilirubinemia requiring phototherapy were enrolled. Paired TcB and TSB measurements were obtained before phototherapy, during phototherapy, and 12 hours after its discontinuation. TcB was measured from the protected forehead using a Dräger JM-105 bilirubinometer, while TSB was determined from venous blood samples using an automated biochemical analyser. Quantitative variables were presented as mean ± standard deviation, while categorical variables were expressed as frequencies and percentages. Paired-samples t-tests were used to compare TcB and TSB values at each assessment stage. Subgroup analyses were performed according to gestational age and birth weight, with p<0.05 considered statistically significant.

Results: A total of 199 jaundiced preterm neonates were evaluated. Before phototherapy, the mean paired difference between TSB and TcB was −16.00 ± 19.64, indicating that TcB tended to overestimate TSB (t=−11.491, p<0.001). During phototherapy, the mean difference increased to 45.49 ± 25.86, demonstrating substantial underestimation of TSB by TcB (t=24.817, p<0.001). Twelve hours after phototherapy discontinuation, the mean difference decreased to 5.81 ± 21.27 but remained statistically significant (t=3.853, p<0.001). The wide standard deviations indicated considerable interindividual variability in the agreement between the two methods.

Conclusion: TcB measurements showed significant differences from TSB before, during, and after phototherapy. The greatest discrepancy occurred during phototherapy, when TcB substantially underestimated serum bilirubin levels. TcB may support non-invasive bilirubin screening and follow-up, particularly after phototherapy, but it should not replace TSB measurement when treatment decisions are required in preterm neonates.