What does the liver function panel include?

Generally, the five items of liver function tests include alanine aminotransferase (ALT), aspartate aminotransferase (AST), total bilirubin, direct bilirubin, and indirect bilirubin. The detailed analysis is as follows:

1. Alanine Aminotransferase (ALT)

Alanine aminotransferase primarily exists within liver cells and is a sensitive indicator of liver cell damage. When liver cells are damaged, ALT is released into the bloodstream, which may cause elevated levels of ALT in the blood. Therefore, measuring ALT levels can help determine whether liver cells are damaged.

2. Aspartate Aminotransferase (AST)

Aspartate aminotransferase is also present in liver cells but is widely distributed in other tissues such as the heart muscle and skeletal muscles. When the liver or other tissues are damaged, AST is released into the bloodstream. Although it is less specific than ALT, when used in combination with ALT testing, it provides a more comprehensive assessment of the extent of liver damage.

3. Total Bilirubin

Total bilirubin is the sum of direct bilirubin and indirect bilirubin, and is used to determine the presence and degree of jaundice. When liver function is impaired, the metabolism and excretion of bilirubin are affected, leading to elevated total bilirubin levels. Jaundice is one of the common manifestations of impaired liver function.

4. Direct Bilirubin

Direct bilirubin is the processed form of bilirubin by liver cells. It is water-soluble and can be excreted from the body through the kidneys. An increase in direct bilirubin typically indicates impaired excretion of bilirubin by the liver and may be caused by diseases such as hepatitis, cirrhosis, or liver cancer.

5. Indirect Bilirubin

Indirect bilirubin is the unprocessed form of bilirubin, primarily derived from aged red blood cells. Elevated levels of indirect bilirubin may result from hemolytic anemia, iron deficiency anemia, or an overactive spleen, and may also be related to disorders of bilirubin metabolism caused by liver disease.

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