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ID:37 Bilirubin (conjugated/direct)
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DescriptionA breakdown product of haemoglobin metabolism.
IndicationInvestigation of jaundice in the first 48 hr, unresolved jaundice post 10 days and suspected high levels of bilirubin during the first 2 weeks.
Additional InfoUNCONJUGATED HYPERBILIRUBINAEMIA: Unconjugated bilirubin is lipid soluble and can cross the blood brain barrier where its toxic effects cause irreversible brain damage (kernicterus). Severe hyperbilirubinaemia is treated first with phototherapy and then with exchange transfusion. PHYSIOLOGICAL JAUNDICE - Transient unconjugated hyperbilirubinaemia presenting with jaundice on the 2nd or 3rd day of life and persisting for 2 weeks. In the premature infant physiological jaundice may last as long as 4 weeks. Neonates have increased levels of unconjugated bilirubin. This is a result of the increased synthesis of bilirubin (due to the decreased half life of red cells and the presence of large amounts of red cell precursors) and the reduced clearance (due to reduced membrane uptake and ligand production, immaturity of the enzyme UDP glucuronyl transferase which is involved in hepatic conjugation, inefficient bile acid metabolism and transport). In cases of persistent neonatal unconjugated hyperbilirubinaemia consider other pathological causes such as haemolytic disease (Rhesus incompatibility, deficiency of the enzyme glucose 6-phosphatase dehydrogenase, toxins,infection), Gilbert's syndrome, Crigler-Najjar (inherited disorder of bilirubin conjugation). CONJUGATED HYPERBILIRUBINAEMIA: Defined as a conjugated plasma bilirubin > 15% of total. Tends to be characterised by pale stools and dark urine. Can be intra or extra hepatic. ALP tends to be raised in extrahepatic causes. In neonates consider biliary atresia as an extrahepatic cause.
Concurrent Testsna
Dietary Requirementsna

InterpretationJaundice in 1st 48 hrs indicative of haemolytic disease. Jaundice persisting for > 10 days - consider IEM screen, TFT's, AAT deficiency, IgM. Danger of kernicterus > 300 umol/L but also consider albumin level, drugs, pH which affect unbound bilirubin.

Ref. Range (Male)see note
Ref. Range (Female)
Ref. Range (Paed)
Ref. Range Notes<20 % of Total Bilirubin and >18 umol/L
Unitsumol/L


IP Acute TATRefer to Website
IP Routine TATRefer to Website
GP Acute TAT- Contact Laboratory
GP Routine TATRefer to Website
Turnround CommentNA
Originally edited by : JHB. Last edited on 04/11/2015 11:26:36. Published By SB on 04/11/2014 11:26:36.