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Liver Function Screening

ALT/AST An initial step in detecting liver damage, is a simple blood test to determine the presence of certain liver enzymes in the blood. Under normal circumstances, these enzymes reside within the cells of the liver. But when the liver is injured, these enzymes are spilled into the blood stream signaling liver damage. Among the most sensitive and widely used of these liver enzymes are the aminotransferases. They include AST or SGOT and ALT or SGPT.

AST (SGOT) is normally found in a diversity of tissues including liver, heart, muscle, kidney and brain. It is released into serum when any one of these tissues is damaged. It is not a highly specific indicator of liver injury.

ALT (SGPT) is not exclusive to the liver, but that is where it is most concentrated. It is released into the bloodstream as a result of liver injury. It serves as a fairly specific indicator of liver status.

The most common cause of mild to moderate elevations of these liver enzymes is fatty liver. In the United States the most frequent cause of fatty liver is alcohol abuse. Other causes include diabetes mellitus and obesity. Additionally, chronic hepatitis C is also becoming an important cause of mild to moderate elevations.

A host of medications can cause abnormal liver enzyme levels.

Examples include:

• Pain relief medications such as aspirin, acetaminophen, ibuprofen, naproxen, diclofenac and phenybutazone.
• Anti-seizure medications such as Dilantin, Tegretol and Phenobarbital.
• Antibiotics such as the tetracyclines, sulfonamides, isoniazid (INH), sulfamethoxazole, etc.
• Cholesterol-lowering drugs such as the statins and niacin. 
• Cardiovascular drugs.
• Anti-depressant drugs of the tricyclic type.