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Hepatitis Blood Test Results

There are five known viruses that cause hepatitis. All can be detected by measuring the levels of antibodies or liver enzymes in the blood. Some antibodies last a few weeks in the blood, while others are detectable for months or years after the initial infection. Knowing when these antibodies and enzymes are detectable helps to understand when the infection occurred and if a patient is infectious.

  1. Hepatitis Blood Tests

    • Hepatitis is a disease of the liver caused by any one of five viral infections. One of the first indicators of hepatitis is an increase in the levels of liver enzymes AST and ALT in the blood. These enzymes are released into the blood when the liver's cells are broken down. If the hepatitis is a result of an infection, antibody levels against the specific viruses are produced. These antibodies come in two classes, IgM and IgG. IgM antibodies show up earlier in the infection and last a few weeks in the blood. IgG antibodies show up later, but they last for months or years in the blood.

    Hepatitis A

    • Hepatitis A is a viral disease caused by the hepatitis A virus (HAV), a food- and water-borne virus. HAV causes an increase in the liver enzymes and the appearance of IgM antibodies about a week after being exposed to the virus. IgM levels then drop down to undetectable levels after 13 weeks. IgG antibodies appear about two weeks after being exposed to the virus and remain detectable for years. Knowing the liver enzyme and antibody levels helps determine the approximate date of infection and how long a patient is infectious to others.

    Hepatitis B

    • The hepatitis B virus (HBV) is a blood-borne virus that causes hepatitis B infection. The first marker of the disease to be detected in blood is the hepatitis B surface antigen (HBsAg), which appears about four weeks after infection and lasts for two months. Hepatitis B virus DNA is also detectable during the same time. At around three to 15 weeks, the hepatitis B envelope antigen (HBeAg) appears and is indicative of acute disease. Shortly after the HBeAg is no longer detected, antibodies against it appear and last for months or years. IgM antibodies against the hepatitis B core antigen (HBcAg) appear around three weeks after the infection, right around the time of symptoms. IgG antibodies against HBcAg last for months or years. Antibodies against the HBsAg appear at about 32 weeks after the infection and last indefinitely.

    Hepatitis C

    • Hepatitis C is caused by the hepatitis C virus (HCV), another blood-borne virus. Acute HCV infection is detected by elevated ALT liver enzyme levels. Antibodies against the virus do not appear for up to two months after infection, and only about 20 percent of those infected feel any symptoms. So the liver enzyme levels become key in detecting the infection, while HCV RNA, which appears in the blood about three weeks after infection, is used to confirm the diagnosis. However, the presence of RNA without elevated enzymes is usually indicative of chronic disease.

    Other Hepatitis Infections

    • Hepatitis D, a blood-borne infection, and hepatitis E, a water- and food-borne infection, are both also detected by antibodies against the specific viruses combined with elevated liver enzyme levels. The presence of antibodies alone is only indicative of exposure to the viruses. So a combination of antibodies and enzyme levels are needed for an accurate diagnosis.

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