Assessing the risk of developing severe hyperbilirubinemia, based on a nomogram has been recommended by the American Academy of Pediatrics(10). The objectives of this study were: 1) To develop an hourspecific nomogram, using transcutaneous bilirubin level (TCB, Bilicheck, SpecRx, Inc, Norcross, GA, USA), in Thai newborn infants and 2) To determine the risk zones that will predict the development of severe hyperbilirubinemia.
Three hundred and ninety two (392) healthy neonates, born by C-section, were recruited from November 2003 to May 2004. One hundred and eight (108) infants were excluded from the nomogram development due to hemolytic diseases (ABO incompatibility 51, G6PD deficiency 34, combined ABO incompatibility and G6PD deficiency 3) and requirement of phototherapy (20). Nomogram, using daily hourspecific TCB for 4 days, of 284 neonates was constructed. Plotting all 392 infants, TCB on the nomogram, the risk zones in relation to the requirement of phototherapy was determined. The 90th percentile (P90) was designated as high risk track with the sensitivity of 96.9%, specificity 78.8%, positive and negative predictive values 29.1% and 99% respectively, and LR 4.6. P10 was labeled as very low risk track, area between P10-P25 as low risk zone, P25-P90 as intermediate zone with P25-P50 as low intermediate and P50-P90 as high intermediate. In conclusion, an hour-specific TCB nomogram, can be used to identify the risk of subsequent development of severe hyperbilirubinemia. Recognizing the infant’s risk enables awareness of the problem
and prompt intervention which should reduce severe hyperbilirubinemia and chance to develop bilirubin encephalopathy.

Keywords: Nomogram, Jaundice, Hyperbilirubinemia, Transcutaneous bilirubin, Newborn infants