Does the Site of Measurement Affect Diagnostic Accuracy of Transcutaneous Bilirubin in Preterm Neonates? A Prospective Study From India

Aim This study aimed to compare the diagnostic accuracy of transcutaneous bilirubin (TcB) measurements obtained from three different skin sites with total serum bilirubin (TSB) levels in preterm neonates before initiating phototherapy and to determine which site more accurately reflects TSB. Methods This prospective study was conducted in the neonatal unit. Transcutaneous bilirubin levels were measured using a Drager JM‐105 bilirubinometer at three different skin sites—forehead, sternum, and interscapular area. Simultaneously, total serum bilirubin (TSB) was estimated using the diazo method. Neonates were excluded if they had poor perfusion, skin lesions at any of the measurement sites, or prior exposure to phototherapy. Phototherapy for preterm neonates was initiated according to the standard NICU protocols. Appropriate statistical analyses were employed. Results A total of 138 preterm neonates who developed jaundice within the first 14 days of life were enrolled. Transcutaneous bilirubin readings from all three skin sites showed significant correlation with TSB ( p < 0.001), with the best correlation at the interscapular site. This site showed the highest area under the ROC curve (AUC 0.938) and highest Pearson correlation coefficient ( r = 0.875). The TcB‐TSB differences ranged from −2.5 to +3.2 mg/dL at the forehead, −2.5 to +1.9 mg/dL at the interscapular site, and −2.5 to +1.8 mg/dL at the sternum. Compared to the forehead and sternum, the interscapular site demonstrated less negative mean bias, indicating a lower tendency to underestimate TSB. Scatter plots also revealed a stronger linear correlation at this site. The diagnostic performance of TcB was evaluated at all three sites using a TSB threshold of 10 mg/dL. Amongst them, the interscapular site showed the highest sensitivity (97.6%, 95% CI: 93.1–100), specificity (96.8%, 95% CI: 91.9–99.6), and the lowest false‐negative rate (11.4%). Conclusion In preterm neonates with jaundice, the interscapular site provides a more reliable estimate of transcutaneous bilirubin compared to the forehead and sternum.