Synonyms

   Unconjugated bilirubin

Clinical Significance

   Indirect bilirubin is the difference between total and direct bilirubin. Common causes of higher indirect bilirubin include: Hemolytic anemia. This means your body is getting rid of too many red blood cells. Bleeding into the skin caused by injury.

Specimen

   Serum

Stability

   Refrigerated (preferred) : 24 hours (LIGHT PROTECTED specimen container)

   Frozen : 30 days (LIGHT PROTECTED specimen container)

   Ambient : 6 hours (LIGHT PROTECTED specimen container)

Reference Range

   0.2 – 0.9 mg/dL

Interpretation

   Indirect bilirubin levels must be assessed in conjunction with total and direct levels and the clinical setting. Indirect (unconjugated) bilirubin levels can increase due to:

       Gilbert’s syndrome. This benign syndrome is due to an inherited gene mutation that mildly increases bilirubin levels. Up to 16 % of all people have this syndrome. Bilirubin levels may spike when exposed to stress [15, 16]

       Strenuous exercise. Athletes can normally have elevated bilirubin levels [17, 18]

       Abnormal red blood cell destruction (hemolysis) [19]

       A reaction to blood transfusion [20]

       Liver diseases such as cirrhosis and fatty liver [21, 22]

       Some rare genetic disorders (e.g. Crigler-Najjar syndrome) [23, 24]

       Antiviral drug atazanavir

Limitation

   Specimens should be protected from light and analyzed as soon as possible; grossly hemolyzed specimens should be rejected because hemoglobin inhibits the diazo reaction and falsely low results may be seen.