Correlation of transcutaneous bilirubinometry (TcB) and total serum bilirubin (TsB) levels after phototherapy

Aim: To investigate the correlation between transcutaneous bilirubinometry (TcB) and total serum bilirubin (TsB) in jaundiced infants before and after, but not during phototherapy. Methods: This study prospectively investigated the correlation between TcB and TsB in term and near term infants before and after phototherapy. Results: Overall 673 pairs of measurements (TcB and TsB) were performed on 371 infants of ≥35 weeks gestation and with birth weight above 2000 g. Of these 337 sets were from 200 infants who had not been treated with phototherapy (Group 1) and 336 measurements from 171 infants taken between 1 h and 5 d after phototherapy (Group 2). The correlation coefficient between TcB and TsB in the whole cohort was r = 0.72. The correlation was low during the first 8 h after phototherapy (r = 0.56), but thereafter the correlation returned to the range of 0.65-0.8. Using the Sobel test, no significant difference was found between the correlation coefficients at the different time periods, with the possible exception of the difference between 1 and 8 h and 9 and 16 h which was of borderline significance with a p value of 0.06. Conclusion: This study demonstrates good correlation between TcB and TsB by 8 h after phototherapy. This adds validity to community-based screening programs employing TcB measurements plotted on TsB nomograms. Such programs may contribute to prevention of tragic cases of bilirubin-induced neurologic damage.