Indirect bilirubin

Intermediate bilirubin test

Note: indirect bilirubin is a calculated parameter. To obtain the test result, it is necessary to purchase total bilirubin and direct bilirubin.

Bilirubin is an orange pigment, a decomposition product of heme, a component of hemoglobin - a substance that enables oxygen transfer in red blood cells (erythrocytes).

Erythrocytes live for 120 days. As a result of their breakdown (multi-step transformation of heme), bilirubin (free, intermediate, unconjugated) is released into the bloodstream and binds to the blood carrier protein, albumin. This form of bilirubin is insoluble in water.

Along with albumin, free bilirubin is carried to the liver. There, glucuronic acid is attached to it and bound (conjugated, direct) bilirubin is formed. It is secreted into the bile and with it passes from the liver to the small intestine, where it is further broken down by bacteria and eventually excreted in the feces.

Laboratory tests measure both the level of total bilirubin, as well as free (in the blood with albumin) and bound (in the liver or bile, with glucuronic acid).

An increase in bilirubin levels above 2.5mg% manifests as jaundice (a yellow coloration of the sclerae, mucous membranes and skin).

An increase in the level of free bilirubin is usually associated with the processes of excessive breakdown of red blood cells, while that associated with liver dysfunction (the efficiency of the process of conjugating bilirubin with glucuronic acid or secreting it into bile).

Intermediate bilirubin - when to perform the test?

Bilirubin is tested to see how the liver is functioning. Measurement of its concentration is useful when liver damage is suspected.

The test is also useful in diagnosing jaundice and differentiating its cause. It is performed when hemolytic jaundice, or jaundice associated with excessive breakdown of red blood cells, is suspected.

The test is also useful in diagnosing jaundice

Additionally, measurement and monitoring of bilirubin levels in newborns with jaundice is part of the standard of postnatal medical care for the child.

Intermediate bilirubin - who should perform the test?

Any patient with symptoms that may suggest liver disease:

• hidrosis
• dark urine
• light stools
• abdominal pain
• discharge, general weakness

The assay is useful when liver damage is suspected, in patients with a history of excessive drinking, those showing signs of drug toxicity or those exposed to the hepatitis virus. It is usually performed as part of a liver panel (along with measurement of aminotransferase activity, LDH, albumin concentration).

The test may also prove useful in patients with suspected hemolytic anemia (a process of breakdown of red blood cells), reporting:

• yellowing
• abnormal urine color
• dark stools
• abdominal pain
• fast heartbeat
• discomfort

In this case, tests to assess the status of the red blood cell system (red blood cell count, hemoglobin, haptoglobin, reticulocytes, activity LDH) are often ordered along with a bilirubin level determination.