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Bilirubin Direct

Order Code CH121
Turnaround Time 24 hours
Test Includes

Bilirubin Direct

Specimen Requirements
Specimen Source
Transport Container
(Specimen Container)

SST (Tiger Top)
Lithium Heparin/ Sodium Heparin/ EDTA

Preferred Specimens
Minimum Volume (uL)
.5 mL
Collection Instructions
(Transport Temperature)
Specimen Stability
Temperature Period
Room temperature 2 days
Refrigerated 7 days
Frozen 3 months (-80°C)
Test Details
Diazo Reaction
Clinical Significance

Red blood cells at the end of their circulating life are broken down in the reticuloendothelial system, mainly the spleen. The resulting heme, once the iron is removed, is then converted to bilirubin. This process accounts for about 80% of the 500 μmol (300 mg) of bilirubin formed daily. Other sources of bilirubin include the breakdown of myoglobin and cytochromes and the catabolism of immature red blood cells in the bone marrow. Once formed, bilirubin is transported to the liver bound to albumin. This fraction of bilirubin is referred to as indirect or unconjugated bilirubin. In the liver, bilirubin is conjugated to glucuronic acid (mono- and diglucuronides) to form conjugated bilirubin by the enzyme uridyl diphosphate glucuronyl transferase. Conjugated bilirubin or direct bilirubin is excreted via the biliary system into the intestine, where it is metabolized by bacteria to a group of products known collectively as stercobilinogen. Elimination is almost complete and serum levels are normally negligible. Direct bilirubin is the sum of the conjugated fractions. Direct bilirubin is elevated in conditions causing hepatic obstruction, hepatitis, cirrhosis, several inherited enzyme deficiencies, and inherited defects in canalicular excretion.

Reference Ranges

0.0 – 0.4 mg/dL (0 Days – 14 Days)
0.0 – 0.5 mg/dL (14 Days – No Max Age Limit)