Hepatitis - Diagnosis

Highlights	Hepatitis B and D	Outlook
Introduction	Hepatitis C	Resources
Diagnosis	Autoimmune Hepatitis	References
Hepatitis A	Symptom Management

Diagnosis

In people suspected of having or carrying viral hepatitis, physicians will measure certain substances in the blood.

Bilirubin. Bilirubin is one of the most important factors indicative of hepatitis. It is a red-yellow pigment that is normally metabolized in the liver and then excreted in the urine. In patients with hepatitis, the liver cannot process bilirubin, and blood levels of this substance rise. (High levels of bilirubin cause the yellowish skin tone, known as jaundice.)
Liver Enzymes (Aminotransferases). Enzymes known as aminotransferases, including aspartate (AST) and alanine (ALT), are released when the liver is damaged. Measurements of these enzymes, particularly ALT, are the least expensive and most noninvasive tests for determining severity of the underlying liver disease and monitoring treatment effectiveness. Enzyme levels vary, however, and are not always an accurate indicator of disease activity. (For example, they are not useful in detecting progression to cirrhosis.)

Blood is drawn from a vein (venipuncture), usually from the inside of the elbow or the back of the hand. A needle is inserted into the vein, and the blood is collected in an air-tight vial or a syringe. Preparation may vary depending on the specific test.

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General Tests to Determine Causes of Viral Hepatitis

Radioimmunoassays. To identify the particular virus causing hepatitis, blood tests called radioimmunoassays are performed. Typically, radioimmunoassays identify particular antibodies, which are molecules in the immune system that attack specific antigens. (Antigens are any molecules that the body considers threatening or dangerous and which can be targeted by antibodies.) Some of these tests can pinpoint hepatitis antigens directly. These tests, however, have limitations:

There may not be sufficient numbers of antibodies to be detectable by blood tests for up to weeks or months after hepatitis develops. Blood tests that are taken too early, then, may miss these signs of infection.
Antibodies also persist after patients recover, so a positive antibody test can indicate a previous infection but does not necessarily determine if the infection is active.

The assays for individual hepatitis viruses may differ.

Polymerase Chain Reaction. In some cases of hepatitis C, a polymerase chain reaction (PCR), may be performed. PCR is able to make multiple copies of the virus? genetic material to the point where it is detectable.