Bilirubin (conjugated), Plasma

Diagnostic Use

Conjugated bilirubin refers to the fraction of bilirubin that has undergone hepatic conjugation with glucuronic acid.

Blood levels of conjugated bilirubin rise when there is an obstruction to biliary drainage. Conjugated bilirubin may be measured to determine the likely cause of hyperbilirubinaemia in a patient with undifferentiated jaundice.

Department

Core Biochemistry

Delphic Registration Code

CBIL

Laboratory Handling

Test Adds

Sample stability - 72 hrs

Synonyms

Conjugated bilirubin
Direct bilirubin

Turnaround Time

3 hours

Test Code

3526

Specimen Type

• Serum
• Plasma

Specimen Requirements

Tube/Container Type:

Preferred

• Lithium Heparin - Non-gel (Green Cap)

Acceptable

• Serum (Red Cap)
• SST II (Gold Cap)
• Lithium Heparin - Gel (Light Green Cap)

Preferred Sample Volume (ml)

4.5

No of Samples Required

1

Pre-testing Requirements

Specimens should be protected from light before analysis

Additional Specimen Information

Paediatric Specimen: Heparin microtainer tube 600 µL

Aliquot Instructions

Sample Type

• Serum
• Plasma

Minimum Volume (ml)

0.1

Transport to Lab

Ambient (8 - 24 degrees Celsius)

Interpretation

In normal health, most of the bilirubin in the plasma is unconjugated.  In cholestasis (i.e. impaired bile flow) there is backflow of conjugated bilirubin into the circulation.

The causes of hyperbilirubinaemia can be split into pre-hepatic, hepatic and post-hepatic categories.  Measurement of total bilirubin and conjugated bilirubin may help to differentiate between these categories.

– In pre-hepatic jaundice (e.g. haemolysis), the conjugated bilirubin is unlikely to be significantly elevated.

– In hepatic jaundice (e.g. hepatitis), there may be a mixed picture with elevations of both unconjugated and conjugated fractions.  Results vary according to the specific underlying cause.

– In post-hepatic jaundice (e.g. cholestasis), the conjugated bilirubin is likely to be predominantly elevated, with a smaller elevation in unconjugated bilirubin also possible.

In neonatal jaundice, an elevated conjugated bilirubin is indicative of an underlying pathological cause (e.g. biliary atresia).

Conjugated bilirubin may be degraded by exposure to light.  Specimens should therefore be protected from light.

Reference Intervals

0 – 5 umol/L

Test Method

Photometric colour test for the quantitative determination of direct bilirubin on Beckman Coulter AU5822 analyser.

Non-Funded Test Cost

$3.24 (Exclusive of GST)

Billing Code

3526

Contact Information

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