Bilirubin (Direct)

Overview

Direct bilirubin measures the conjugated fraction of bilirubin in the blood, which is processed by the liver and excreted into bile. It indicates liver conjugation capacity and biliary excretion efficiency. Elevated levels suggest intrahepatic or extrahepatic cholestasis, Dubin-Johnson syndrome, or Rotor syndrome, while low levels are typically insignificant. It is clinically useful for differentiating conjugated from unconjugated hyperbilirubinemia in jaundice evaluation.rupahealth+1

Clinical Use Cases

  • Distinguishing cholestatic from hepatocellular jaundice.
  • Diagnosing biliary obstruction (e.g., gallstones, tumors).
  • Evaluating liver diseases like primary biliary cholangitis.
  • Assessing conjugated hyperbilirubinemia in neonates.

Specimen Types

  • Serum.
  • Plasma.
  • Whole blood (point-of-care devices).

Measurement Methods

  • Jendrassik-Grof method (diazo reaction).
  • Enzymatic assays.
  • Spectrophotometric analysis.

Test Preparation and Influencing Factors

  • No fasting required.
  • Hemolysis or lipemia can interfere.
  • Certain drugs (e.g., rifampin) may elevate levels.
  • Physiological: higher in neonates; diurnal variation minimal.

Synonyms

  • Conjugated bilirubin.
  • Direct-reacting bilirubin.
  • DBIL.

Further Reading