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Liver
Direct (conjugated) bilirubin
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This is the date the draft was written, not a medical review date.
The water-soluble fraction conjugated with glucuronic acid in the hepatocyte and excreted in bile. A raised direct fraction indicates impaired hepatic excretion or biliary obstruction.
Reference interval
| Conventional (mg/dL) | SI (µmol/L) | |
|---|---|---|
| Adults | 0–0.3 mg/dL | 0–5.1 µmol/L |
Specimen: Serum (protect from light) · Conventional × 17.1 = SI
Causes of high values
Biliary obstruction (gallstones, pancreatic head tumour), cholestatic and hepatocellular liver disease, Dubin-Johnson and Rotor syndromes, drug-induced cholestasis, sepsis.
Causes of low values
Not clinically significant.
Pre-analytical and method notes
The diazo method overestimates the direct fraction and some laboratories report only total bilirubin, with the direct fraction added when total is raised. The direct fraction is normally below about 20 % of the total. Reference intervals vary by laboratory, method and population; use the interval printed on the report.
References
- Rifai N, Horvath AR, Wittwer CT. Tietz Textbook of Clinical Chemistry and Molecular Diagnostics. Elsevier, 6th edition (2018) — Tier 3 (textbook)
- McPherson RA, Pincus MR. Henry's Clinical Diagnosis and Management by Laboratory Methods. Elsevier — Tier 3 (textbook)
- Sleisenger and Fordtran's Gastrointestinal and Liver Disease. Elsevier, 11th edition (2020) — Tier 3 (textbook)
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