Correlation of Total Serum Bilirubin and Transcutaneous Bilirubin at Different Sites in Term Neonates: Impact of Phototherapy

Abstract Objective: To evaluate the correlation between total serum bilirubin (TSB) and transcutaneous bilirubin (TcB) at different sites in term neonates before, during, and after phototherapy. Methods: This cross-sectional observational study was conducted at a tertiary care teaching hospital in western Rajasthan from June–December 2022. Term neonates (≥37 weeks) requiring phototherapy were included. TSB was estimated using the Diazo method at baseline, 24 hours after initiation, and 24 hours after completion of phototherapy. Corresponding TcB readings were taken at the sternum (exposed), glabella (eye-shield covered), and pubic symphysis (diaper-covered) using Drager JM-105. Correlation was analyzed using Pearson’s coefficient, and agreement assessed with Bland–Altman plots. Results: Of 850 neonates screened, 130 met inclusion criteria. Before phototherapy, TcB correlated strongly with TSB at the sternum (r = 0.96), with minimal overestimation (bias +0.3 mg/dL). During phototherapy, TcB underestimated TSB, with strongest correlation at the sternum (r = 0.91) and least bias at the pubic symphysis (−0.83 mg/dL). After phototherapy, TcB correlation was highest at the sternum (r = 0.98), with minimal underestimation at the pubic symphysis (−0.11 mg/dL). Conclusions: TcB correlated well with TSB before, during, and after phototherapy. While TcB tended to overestimate TSB before treatment and underestimate it during/after, covered sites such as the pubic symphysis provided reliable measurements, supporting their use in clinical practice.