Transcutaneous bilirubin estimation in extremely low birth weight infants receiving phototherapy: a prospective observational study

BACKGROUND: Measurement of transcutaneous bilirubin (TcB) is a quick, reliable and painless method to guide management of hyperbilirubinemia. Studies in term and late preterm infants have found that TcB measurements from covered areas (TcB-C) during phototherapy (PHT) co-relate well with serum bilirubin levels. Limited data exists in extremely low birth weight (ELBW) infants. METHODS: In this prospective observational study, an opaque patch was placed on the back of an ELBW infant prior to initiation of PHT. TcB-C and TcB-E (TcB from exposed area) levels were measured at birth and at 24-h intervals for 5 days. Total serum bilirubin (TSB) levels were also measured within 30 min of obtaining TcB levels. A Wilcoxon signed rank test was used for data analysis. A mixed effect model was used to adjust for repeated measurements over time. The p value < 0.05 was considered significant. RESULTS: A total of 19 infants were enrolled in the study, with a mean gestational age of 26 ± 2 weeks and mean weight 827 ± 127 g. The difference between TcB-C and TSB was 2.68 ± 2.41 mg/dl (mean ± SD, p < 0.001). In contrast, the difference between TcB-E and TSB was − 0.51 ± 1.74 mg/dl (p = 0.02). TcB-C consistently overestimates TSB, while TcB-E consistently underestimates TSB. CONCLUSIONS: During PHT exposure, TcB-C does not correlate with TSB values in ELBW infants. TcB-C levels cannot be used as a surrogate for TSB measurement in ELBW infants.