Objective To determine the diagnostic accuracy of bilirubin levels at age 24 h in predicting severe neonatal hyperbilirubinemia.

Methods A total of 140 full-term normal newborns were enrolled in a prospective study at Siriraj Hospital. For each newborn, the serum bilirubin level was determined at age 24 h. The newborns were followed up for the development of severe hyperbilirubinemia until discharge. The cut-off point of the serum bilirubin level at 24 h was >7.5 mg/dl. Sensitivity, specificity, positive and negative predictive values and accuracy of bilirubin levels at age 24 h in the diagnosis of severe neonatal hyperbilirubinemia were determined.

Results Severe neonatal hyperbilirubinemia was found in 35%. The bilirubin levels at 24 h using a cut-off of >7.5 mg/dl yielded sensitivity of 85.7%, specificity of 72.6%, positive predictive value of 62.7%, negative predictive value of 90.4% and accuracy of 77.1% in the diagnosis of severe neonatal hyperbilirubinemia.

Conclusion Bilirubin levels at age 24 h could predict severe neonatal hyperbilirubinemia that required phototherapy with 85.7% sensitivity and 72.6% specificity.