Diagnosis:

Doctors diagnose hepatitis based on a physical examination and the results of blood tests. In addition to specific tests for hepatitis antibodies, doctors will order other types of blood tests to evaluate liver function.

Specific Tests for Hepatitis A

Blood tests are used to identify IgM anti-HAV antibodies, substances that the body produces to fight hepatitis A infection.

Specific Tests for Hepatitis B

There are many different blood tests for detecting the hepatitis B virus. Standard tests include:

• Hepatitis B surface antigen (HBsAg). A positive result indicates active infection, either acute or chronic.
• Antibody to hepatitis B core antigen (Anti-HBc). A positive result indicates either recent infection or previous infection.
• Antibody to HBsAg (Anti-HBs). A positive result indicates immunity to hepatitis B either from having been infected with the virus in the past or having had received the vaccine.
• Hepatitis E surface antigen (HBeAg) indicates that someone with a chronic infection is more contagious.

Specific Tests for Hepatitis C

Tests to Identify the Virus. The standard first test for diagnosing hepatitis C is known as enzyme-linked immunosorbent assay (ELISA), which is used to test for hepatitis C antibodies. Antibodies can usually be detected by ELISA 4 - 10 weeks after infection.

Tests to Identify Genetic Types and Viral Load. Additional tests called hepatitis C virus RNA assays may be used to confirm the diagnosis. They use a polymerase chain reaction (PCR) to detect the RNA (the genetic material) of the virus. Such tests should be used if ELISA results show positive HCV antibody and may be performed if there is some doubt about a diagnosis but the doctor still firmly believes the virus is present. HCV RNA can be detected through blood tests as early as 2 - 3 weeks after infection.

Hepatitis C RNA assays also determine virus levels (called viral load). Such levels do not reflect the severity of the condition or speed of progression, as they do for other viruses, such as HIV. However, high viral loads may suggest a poorer response to treatment with interferons.

Patients with detectable viral loads should have HCV genotyping perform. Knowing the specific genotype of the virus is helpful in determining a treatment approach. There are six main genetic types of hepatitis C and more than 50 subtypes. They do not appear to affect the rate of progression of the disease itself, but they can differ significantly in their effects on response to treatment. Specific genotypes vary in prevalence around the world. Genotype 1 is the most difficult to treat and is the cause of up to 75% of the cases in the U.S. The other common genetic types in the U.S. are types 2 (15%) and 3 (7%), which are more responsive to treatment than genotype 1. People with hepatitis C need to have their genotype tested so that doctors can make appropriate treatment recommendations.

Researchers are working on developing a genetic test to identify patients with chronic hepatitis C who are most at risk of developing cirrhosis. Researchers hope that this experimental test may eventually help doctors decide which patients should receive early treatment with alpha-interferon and ribavirin.

Liver Biopsy. Liver biopsy may be helpful both for diagnosis and for determining treatment decisions. Only a biopsy can determine the extent of injury in the liver. Some doctors recommend biopsies only for patients who do not have genotypes 2 or 3 (as these genotypes tend to respond well to treatment). A liver biopsy in patients with other genotypes may help clarify risk for disease progression and allow doctors to reserve treatment for patients with moderate-to-severe liver scarring (fibrosis). Even in patients with normal alanine aminotrasferase (ALT) liver enzyme levels, a liver biopsy can reveal significant damage.

Tests for Liver Function

In people suspected of having or carrying viral hepatitis, doctors 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.)
• Alkaline Phosphatase (ALP). High ALP levels can indicate bile duct blockage.
• Serum Albumin Concentration. Serum albumin measures protein in the blood (low levels indicate poor liver function).
• Prothrombin Time (PT). The PT test measures in seconds the time it takes for blood clots to form (the longer it takes the greater the risk for bleeding).

Liver Biopsies

A liver biopsy may be performed for acute viral hepatitis caught in a late stage or for severe cases of chronic hepatitis. No laboratory tests for enzyme or viral levels can truly determine the actual damage to the liver. A biopsy helps determine treatment possibilities, the extent of damage, and the long-term outlook.

A biopsy involves a doctor inserting a biopsy fine needle, guided by ultrasound, to remove a small sample of liver tissue. Local anesthetic is used to numb the area. Patients may feel pressure and some dull pain. The procedure takes about 20 minutes to perform.