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Clinical Pathology

Bilirubin: Conjugated (Direct Bilirubin)

By Dayyal Dg.Twitter Profile | Updated: Tuesday, 07 August 2018 09:21 UTC
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Collection of sample

This test is performed with the patient's serum. There is no restriction for a fasting sample. The test can be done by a random blood sample the patient.

About 3 to 5 ml of blood is collected in a plain test tube, and blood is allowed to clot to get clear serum. In infants, the sample may be collected from the heel. The blood sample is centrifuged for 5 to 10 minutes and the serum is separated for the test.

The patient's serum is stable at 4° C for 3 days and protects it from the light.

Note: Bilirubin is photo-sensitive (photo-oxidized) so keep the sample in dark place otherwise false-negative results may obtain.


  • Avoid sample from hemolysis
  • Do not expose the sample to light. Exposure of sample to light may decrease the value.
  • If there is a delay in performing the test then keep the sample in dark and refrigerate it.
  • Avoid shaking of the test tube as it may lead to an inaccurate result.


  • Serum bilirubin is a very useful test to evaluate liver functions. Raised level of bilirubin can be seen in the hepatic and post-hepatic type of jaundice.
  • Clinically jaundice appears when the level of bilirubin is more than 2 mg/dl.
  • Direct (or conjugated) bilirubin: It is water-soluble and dissolves in water and is synthesized in the liver form indirect bilirubin.

Normal Values

  • Total bilirubin 0.3 to1.0 mg/dL or 5.1 to 17.0 mmol/L
  • Direct bilirubin 0.1 to 0.3 mg/dL or 1.0 to 5.1 mmol/L
  • Indirect bilirubin 0.2–0.7 mg/dL

Raised level of direct bilirubin is seen in

  • Gallbladder tumors
  • Gallstones
  • Dubin-Johnson syndrome
  • Rotor syndrome
  • Obstruction of extrahepatic ducts or inflammatory scarring
  • Can be resolved by the surgery
  • Drugs may cause cholestasis
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