Bilirubin, direct (conjugated)

What it measures

Direct bilirubin is the water-soluble form that the liver has conjugated with glucuronic acid. A raised level indicates impaired excretion of bile, as seen in liver cell disease or bile duct blockage.

Specimen and preparation

• Specimen: Serum or lithium-heparin plasma
• Tube: Gold top
• Preparation: Protect from light; analyse promptly.

Reference range

Reference ranges differ between laboratories, methods and populations. Always use the range printed on your own lab report.

Causes of high values

• Bile duct obstruction (stones, pancreatic head tumour)
• Hepatitis and cirrhosis
• Cholestatic drug reactions
• Dubin–Johnson and Rotor syndromes
• Biliary atresia in infants

Method

Diazo reaction without accelerator

Good to know

In a newborn, direct bilirubin above about 1.0 mg/dL (or >20% of total) needs prompt investigation for biliary atresia.

Related tests