Which tests measure Direct (Conjugated) Bilirubin?

Direct (Conjugated) Bilirubin is measured in 1 test on BiomarkersLabs.com, including Direct Bilirubin (Conjugated Bilirubin).

Biomarker Reference · D. Bili

What does the Direct (Conjugated) Bilirubin test measure?

Q: What is the reference range for Direct (Conjugated) Bilirubin?

The standard reference range for Direct (Conjugated) Bilirubin is 0.0–0.3 mg/dL (0–5 µmol/L) # REVIEWER FLAG: Confirm LabCorp reference range — some platforms report upper limit as 0.2 mg/dL; range is age-dependent in neonates and differs substantially from adult values. Confirm whether the LabCorp assay used is a diazo-based method (Jendrassik-Grof) or a direct spectrophotometric assay, as methods produce slightly different reference intervals.. Reference ranges vary by laboratory and assay platform — interpret in context of the issuing laboratory's stated range.

Direct (Conjugated) Bilirubin (D. Bili) is a clinical biomarker used in gastrointestinal assessment. Bilirubin is the end-product of haem catabolism, generated primarily from the breakdown of senescent erythrocytes by reticuloendothelial macrophages in the spleen and bone marrow. It is measured in 1 laboratory test on BiomarkersLabs.com.

Reference Range: 0.0–0.3 mg/dL (0–5 µmol/L) # REVIEWER FLAG: Confirm LabCorp reference range — some platforms report upper limit as 0.2 mg/dL; range is age-dependent in neonates and differs substantially from adult values. Confirm whether the LabCorp assay used is a diazo-based method (Jendrassik-Grof) or a direct spectrophotometric assay, as methods produce slightly different reference intervals.
Units: mg/dL, µmol/L
Measured In: 1 test
Category: Gastrointestinal

Functional medicine optimalFunctionally, direct bilirubin should be negligible (approaching zero) in healthy individuals. Levels consistently at the upper end of the reference range (0.2–0.3 mg/dL) in the absence of frank jaundice may warrant monitoring alongside other liver function markers in functional medicine contexts. # REVIEWER FLAG: No established functional medicine optimal range exists for direct bilirubin beyond the standard reference interval — reviewer to confirm whether a functional optimal range is appropriate to document for this marker.

What is Direct (Conjugated) Bilirubin?

Bilirubin is the end-product of haem catabolism, generated primarily from the breakdown of senescent erythrocytes by reticuloendothelial macrophages in the spleen and bone marrow. Unconjugated (indirect) bilirubin is released into the circulation bound to albumin and is transported to hepatocytes, where it is conjugated with glucuronic acid by the enzyme UDP-glucuronosyltransferase (UGT1A1) to form the water-soluble conjugated (direct) form. Conjugated bilirubin is then actively secreted into the bile canaliculi by MRP2 (ABCC2) transporters and excreted via the bile duct into the small intestine, where it is metabolised by gut flora to urobilinogen and stercobilinogen. A small fraction recirculates via enterohepatic circulation and is excreted in urine as urobilin.

Why is Direct (Conjugated) Bilirubin measured?

Direct bilirubin is the fraction measured by direct diazo reaction in the standard bilirubin assay and reflects conjugated bilirubin that has been processed by the liver. Elevation of direct bilirubin — particularly when it constitutes more than 50% of total bilirubin — indicates a hepatobiliary aetiology: impaired biliary secretion into the canaliculus (intrahepatic cholestasis), obstruction of the bile duct system (extrahepatic cholestasis), or hepatocellular disease with impaired bilirubin excretion. It is the critical differentiating fraction between prehepatic (predominantly indirect elevation) and hepatic/posthepatic (predominantly direct elevation) causes of jaundice, and is a mandatory component of any hepatic function panel evaluation.

Reference ranges

Standard reference: 0.0–0.3 mg/dL (0–5 µmol/L) # REVIEWER FLAG: Confirm LabCorp reference range — some platforms report upper limit as 0.2 mg/dL; range is age-dependent in neonates and differs substantially from adult values. Confirm whether the LabCorp assay used is a diazo-based method (Jendrassik-Grof) or a direct spectrophotometric assay, as methods produce slightly different reference intervals.
Functional medicine optimal: Functionally, direct bilirubin should be negligible (approaching zero) in healthy individuals. Levels consistently at the upper end of the reference range (0.2–0.3 mg/dL) in the absence of frank jaundice may warrant monitoring alongside other liver function markers in functional medicine contexts. # REVIEWER FLAG: No established functional medicine optimal range exists for direct bilirubin beyond the standard reference interval — reviewer to confirm whether a functional optimal range is appropriate to document for this marker.
Units: mg/dL, µmol/L

Reference ranges vary by laboratory and assay platform. Interpret in context of the issuing laboratory's stated range.

Tests that measure Direct (Conjugated) Bilirubin

1 test on BiomarkersLabs.com include this biomarker.

BML-GAS-043Comprehensive

Direct Bilirubin (Conjugated Bilirubin)

Direct (Conjugated) Bilirubin reference range in this test: 0.0–0.3 mg/dL (0–5 µmol/L) # REVIEWER FLAG: Confirm LabCorp reference range — some platforms report upper limit as 0.2 mg/dL; range is age-dependent in neonates and differs substantially from adult values. Confirm whether the LabCorp assay used is a diazo-based method (Jendrassik-Grof) or a direct spectrophotometric assay, as methods produce slightly different reference intervals.

Related clinical conditions

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