Bilirubin is a waste product produced by the metabolism of haem. Bilirubin undergoes conjugation with glucuronic acid in the liver before being excreted into the bile where it undergoes further metabolism and enterohepatic recycling. Most of the synthesised bilirubin is eventually excreted in the stool as the pigments stercobilin, mesobilin and urobilin.
The neonatal (paediatric) bilirubin assay is calibrated to measure the high concentrations of bilirubin that are often seen in the first few days of life.
Protect sample from light,
Grossly haemolysed samples unsuitable.
Paediatric Specimen: Heparin microtainer tube 400 µL
Chilled (2 - 8 degrees Celsius)
If overnight - Chilled (2 - 8 degrees Celsius)
Protect from light.
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.
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)
Spectrophotometric determination of colour intensity on Beckman Coulter AU5822 Analyser using in house reagents.
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