What is Hepatitis?
Hepatitis is an inflammation of the liver. Most often, hepatitis is caused by infection with certain viruses. However, liver inflammation can also result from exposure to chemicals, over-the-counter or prescription drugs, heavy alcohol use, inherited diseases, autoimmune disease, or fatty buildup in the liver.
The liver is a vital organ located in the upper right-hand side of the abdomen. It performs many functions in the body, including processing the body’s nutrients, producing bile to help digest fats, synthesizing many important proteins, regulating blood clotting, and breaking down potentially toxic substances into harmless ones that the body can use or eliminate. In severe cases, liver inflammation may interfere with these processes and allow potentially toxic substances to build up.
There are several laboratory tests that may be performed in cases of known or suspected hepatitis.
These tests may fall into one or more of the following categories:
- General chemistry tests to detect liver inflammation and/or damage
- Screening tests to detect viral hepatitis; for example, screening for exposure to hepatitis B or hepatitis C may be done because of increased risk of the disease (use of illegal drugs, multiple sex partners) or at the time of blood donation.
- Tests to help diagnose other underlying causes of hepatitis
- Tests to monitor the progression of liver damage and/or help guide treatment
Acute hepatitis is often suspected and testing done because of the appearance of signs and symptoms, such as fever, loss of appetite, and nausea, often accompanied by dark urine, pale stools, and yellow discoloration of the skin and the whites of the eyes (jaundice).
Chronic hepatitis may have no obvious signs and symptoms and is more commonly detected as a result of abnormal routine laboratory tests. These may include, for example, a comprehensive metabolic panel (CMP), a group of tests frequently ordered as part of a yearly health exam, or a liver panel.
Alanine aminotransferase (ALT)
An enzyme found mainly in the liver. When the liver is damaged, ALT is released into the blood, usually before more obvious signs of liver damage occur, such as jaundice. This makes ALT a useful test for early detection of liver damage. Results are often compared to those of the AST test to help determine the cause of liver injury.
Aspartate aminotransferase (AST)
Also an enzyme found in the liver and a few other organs, particularly the heart and other muscles. The test is most useful in detecting liver damage due to hepatitis and may be elevated more than ALT with exposure to drugs toxic to the liver, cirrhosis, or alcoholism. AST, however, is not specific for the liver and may be increased in conditions affecting other parts of the body. Results are often compared to those of the ALT.
Alkaline phosphatase (ALP)
An enzyme related to the bile ducts but also found in other tissues throughout the body. The ALP test is often increased when bile ducts are blocked but may also be increased with bone disorders.
A waste product made from the breakdown of old blood cells that is ultimately processed by the liver so that it can be eliminated from the body. Bilirubin is a yellow compound that can accumulate when the liver is damaged, causing jaundice and dark urine.
The main protein made by the liver. Since albumin is produced by the liver, its level can decrease with loss of liver function; however, this typically occurs only when the liver has been severely affected. Many other conditions also affect albumin level.
Albumin and all other proteins in blood; may be decreased with severe liver disease.
Depending on the healthcare practitioner and the laboratory, other tests that may be done individually or as part of a liver panel include:
Prothrombin time (PT)
This test may be ordered for a person with hepatitis or suspected hepatitis. Proteins used in the formation of a blood clot (coagulation factors) are mostly produced by the liver, and a prolonged PT may indicate the severity of liver damage.
Gamma-glutamyl transpeptidase (GGT)
An enzyme found in the liver that is very sensitive to changes in liver function. The GGT test helps to differentiate between the causes of an elevated ALP; if GGT is increased, then the elevated ALP is due to liver, not bone disease.
Lactate dehydrogenase (LD)
An enzyme released with cell damage; found in cells throughout the body.
Alpha-feto protein (AFP)
Associated with regeneration or proliferation of liver cells.
While the general tests listed above may help detect hepatitis, they do not determine the underlying cause. Additional testing may be necessary to pinpoint the cause and help direct treatment.
Some examples include:
Acute hepatitis panel
may be used to help detect infection with a hepatitis virus
Autoimmune antibodies (e.g., ANA, ASMA, anti-LKM-1)
associated with autoimmune hepatitis