What are the five items in a routine liver function test?

Generally, the five liver function tests in a routine physical examination refer to alanine aminotransferase (ALT), aspartate aminotransferase (AST), total bilirubin, direct bilirubin, and indirect bilirubin. The details are as follows:

1. Alanine Aminotransferase (ALT)

ALT is primarily present in the cytoplasm of liver cells and is one of the most sensitive indicators of hepatocellular injury. When liver cells are damaged, ALT is released into the bloodstream, leading to elevated levels of ALT in the blood.

2. Aspartate Aminotransferase (AST)

AST is mainly found in cardiac muscle cells, and to a lesser extent in the mitochondria of liver cells. Elevated AST levels may indicate significant liver damage, such as that caused by viral hepatitis, cirrhosis, or other liver diseases.

3. Total Bilirubin

Total bilirubin is the sum of direct and indirect bilirubin and accurately reflects the degree of jaundice. Measuring total bilirubin levels helps initially determine the type and severity of jaundice, providing a basis for further treatment.

4. Direct Bilirubin

Direct bilirubin is a substance produced in the liver from hemoglobin released into the bloodstream when red blood cells die or break down. It primarily reflects the liver's excretory function regarding bilirubin. Elevated direct bilirubin usually indicates problems in the liver's excretion process, such as cholestatic liver disease.

5. Indirect Bilirubin

Indirect bilirubin is generated outside the liver when red blood cells are destroyed. It mainly reflects the liver’s ability to convert indirect bilirubin. Increased indirect bilirubin levels may suggest liver disorders or obstruction of the bile ducts.

By measuring changes in these five parameters, it is possible to preliminarily assess whether liver damage exists, its severity and extent, and whether jaundice or related conditions are present.