SAN FRANCISCO – Tests for hepatitis B surface antigen, surface antibody, core antibody, and type “e” antigen each play an important role in diagnosing infection and level of infectivity, Dr. Tina Q. Tan said at the annual meeting of the American Academy of Pediatrics.
These serologic markers of the hepatitis B virus help distinguish infection with this virus from other hepatitis virus infections, all of which cause nonspecific signs, symptoms, and laboratory findings, said Dr. Tan of Northwestern University, Chicago.
Hepatitis B prodrome can cause malaise, fever, headache, myalgia, vomiting or nausea, and right upper-quadrant pain. Jaundice or hepatomegaly may be seen, but more than half of infections are asymptomatic.
A positive hepatitis B surface antigen (HBsAg) test indicates that the patient is acutely or chronically infected and is immune to the hepatitis B virus or to infection with the virus, either because of vaccination or immunity from recovering from an acute infection. False-positive cases are very rare.
The meaning of a positive hepatitis B core antibody (HBcAb) test depends on the type of antibody. A patient who is IgM positive has recently been infected with the hepatitis B virus. Positivity to IgG antibody could indicate a past infection or a chronic infection with hepatitis B virus.
Dr. Tan suggested a three-step process for initial interpretation of the panel of tests:
▸ If the HBsAg is negative and the HBsAb is positive, then the patient is immune to hepatitis B.
▸ If the HBsAg is positive and the HBsAb is negative, then the patient has either acute or chronic hepatitis B infection.
▸ If the HBsAg and HBsAb are negative and the HBcAb is positive, this could be a false-positive result, or the patient is chronically infected or recovering from acute infection, or may be immune to hepatitis B but the HBsAb level is too low to be detected.
A fourth test, for hepatitis B “e” antigen (HBeAg), is a marker of infectiousness. People with HBeAg have high concentrations of hepatitis B viral DNA and are at high risk of transmitting the infection. The tests may need to be repeated over time to assess the patient's status.
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