Alternative Names direct bilirubin, indirect bilirubin, conjugated bilirubin, total bilirubin, unconjugated bilirubin
Definition This test measures the amount of bilirubin in the blood. Bilirubin is produced by the breakdown of haemoglobin, the oxygen-binding protein in red blood cells. Bilirubin is processed in the liver. If liver cells are damaged, it can escape into the bloodstream.
Who is a candidate for the test? The bilirubin test is usually done when liver or gallbladder disease is suspected. Whenever the bilirubin level is too high, a person develops yellowish discolouration of their eyes and skin, a condition known as jaundice. The presence of jaundice will usually prompt a doctor to order a bilirubin level and other blood tests to determine the cause.
How is the test performed? To measure bilirubin levels, a blood sample is taken from a vein on the forearm or hand. First, the skin over the vein is cleaned with an antiseptic. Next, a strong rubber tube, or tourniquet, is wrapped around the upper arm. This restricts blood flow in the veins in the lower arm and enlarges them. A fine needle is gently inserted into a vein, and the tourniquet is removed. Blood flows from the vein through the needle, and is collected in a vial for testing in the laboratory. After the needle is withdrawn, the puncture site is covered with a bandage for a short time to prevent bleeding.
What is involved in preparation for the test? The doctor will provide specific instructions. Generally, no preparation is required.
What do the test results mean? Normal values for direct bilirubin are (Adult 0 - 8 mmols/L, millimoles per litre). Normal values for total bilirubin are (Adult 2 - 20 mmols/L).
A high level of direct conjugated bilirubin is usually caused by blocked bile ducts or bile transfer. High indirect (conjugated) bilirubin may be caused by haemolysis (red blood cell breakdown) or drugs.
A high level of total bilirubin in newborns is usually due to a liver that has not yet fully matured. High levels may also indicate other kinds of anaemia, which is a low red blood cell count. High bilirubin levels in newborns can also be caused when the body is reabsorbing a large collection of blood outside the blood vessels such as from a deep bruise.
Author: Reviewer: HealthAnswers Australia Medical Review Panel Editor: Dr David Taylor, Chief Medical Officer HealthAnswers Australia Last Updated: 1/10/2001 Contributors Potential conflict of interest information for reviewers available on request
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