Direct Bilirubin

Methodology: 
This direct bilirubin reagent utilizes a variation of the classic method developed by Van den Bergh and Mueller. Direct (conjugated) bilirubin couples directly with a diazonium salt of 3,5-dichloroaniline (DPD) in an acid medium to form azobilirubin. The direct bilirubin in serum is directly proportional to the color development of azobilirubin, which is measured bichromatically at 570/660 nm.
Performed: 
Monday - Friday
Reported: 
Within 24 hours
Purpose and principle: 

Bilirubin is an end product of hemoglobin catabolism. It is conjugated with glucuronic acid in the liver, and the conjugated form is cleared from the circulation by excretion in the bile. Both conjugated (direct) and unconjugated (indirect) forms of bilirubin circulate loosely bound to albumin.

The assessment of direct bilirubin is helpful in the determination of hepatic disorders. The increase in the total bilirubin associated with obstructive jaundice is primarily due to the direct fraction. Both direct and indirect bilirubin are increased in the serum with hepatitis.

In the newborn patient with hemolytic jaundice and neonatal jaundice, the increase in the total bilirubin is primarily due to the indirect bilirubin fraction. This jaundice may becaused by Rh, ABO, or other blood group incompatibilities, by hepatic immaturity, or by hereditary defects in bilirubin conjugation.

Specimen Requirements: 

Type: Peripheral Blood

Container/Tube:
  • Serum, gel
  • Plasma, gel

Sample Volume: 0.5mL serum

Stability (collection to initiation of testing): Specimens should be protected from light.
  • Refrigerated: 3 days
  • Frozen: 3 months
Unacceptable Conditions:
  • Moderate or gross hemolysis
CPT Code (s): 
82248
Notes: 

UFHPL Test #: 82248

UFHPL Epic order code: LAB52

Collection procedure: 
Serum gel tubes should be centrifuged within 2 hours of collection.
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