Interpretation
Total bilirubin results in neonates should be interpreted using a nomogram rather than reference intervals. Refer to local policies and procedures for guidance. A result above the nomogram treatment line is associated with an increased risk of bilirubin encephalopathy (kernicterus) and should be seen as an indication to start treatment with phototherapy or exchange transfusion in severe cases.
Neonatal jaundice is common, affecting at least 50% of babies born at term, with a higher incidence in prematurity and in breastfed babies. Most cases of neonatal jaundice are benign and self-limiting with resolution over 1-2 weeks. However, it is important to exclude pathological causes of jaundice. Causes of pathological jaundice include haemolysis (e.g. Rh incompatibility), sepsis, inborn errors of metabolism and congenital malformative disorders (e.g. congenital biliary atresia).
An elevated conjugated bilirubin is always considered a pathological finding. It is common therefore for babies to have total bilirubin and conjugated bilirubin measured at the same time (sometimes referred to as a “split bilirubin”). If the conjugated bilirubin is normal and there are no features suggestive of a pathological cause, the total bilirubin may be interpreted according to the nomogram, as described above.
Reference Intervals
Treatment nomogram: Gestation 35-37 weeks
Treatment nomogram: Gestation ≥ 38 weeks
(These nomogram are from Canterbury Hospital Health Pathways – check local procedures to ensure that you are using the correct chart for your location)
Test Method
Spectrophotometric determination of colour intensity on Beckman Coulter AU5822 Analyser using in house reagents.