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Hepatitis B test: antibodies to HBSAg (Anti-HBSAg) in blood
Last reviewed: 06.07.2025
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Anti-HB s are normally absent in blood serum.
Antibodies to the surface antigen of viral hepatitis B - anti-HB s - are detected at the end of acute viral hepatitis B or (most often) 3 months after the onset of infection, sometimes later (up to a year), they persist for a long time, on average 5 years. Anti-HB s are not detected immediately after the disappearance of HB s Ag. The duration of the "window" phase varies from several weeks to several months. Antibodies to the surface antigen of viral hepatitis B neutralize the virus, their presence is considered a sign of immunity. They belong to the IgG class. Determination of anti-HB s is of great importance for assessing the course of viral hepatitis B and its outcomes, since it characterizes the immune response of a specific patient. This is a reliable criterion for the development of post-infectious immunity and recovery. Detection of anti-HB s can serve as a criterion for retrospective diagnosis of hepatitis of previously unspecified etiology.
Anti-HB s indicate a previous infection.
Detection of antibodies to HB s plays an important role in determining the contingent for vaccination against viral hepatitis B. According to WHO recommendations, if the level of anti-HB s is less than 10 mIU/l, such persons are indicated for vaccination against viral hepatitis B; at a level of 10-100 mIU/l, vaccination should be postponed for 1 year; at a level of more than 100 mIU/l, vaccination is indicated after 5-7 years.
Blood tests for the presence of antibodies to HB s are performed for the following purposes:
- diagnostics of viral hepatitis B in the late stage of convalescence;
- retrospective diagnosis of previous viral hepatitis B;
- diagnostics of anti-HB S -positive chronic viral hepatitis B;
- diagnosis of persistent chronic viral hepatitis B;
- assessment of the immune response after vaccination with hepatitis B vaccine.
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