Virology Practice Question

A patient presents for pre-employment serology testing. Hepatitis B serology is as follows: anti-HbS positive, Hb surface antigen negative, and total anti-Hb core positive. What is the most likely interpretation?

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Immunity from previous infection — Correct answer

Correct. The serology is anti-Hb surface antigen negative because the virus was cleared from the body. The serology is anti-HbS and anti-Hb core positive from exposure to virus and not just the vaccine. If immunity was due to the vaccine only it would be anti-HbS positive anti-HbC negative.

Chronic infection

Incorrect. This would be Hb S Ag positive, total anti-Hb core positive, IgM anti-Hb core negative, anti-Hb surface negative.

Acute infection

Incorrect. Before the window period, this would be Hb surface antigen positive, anti-Hb surface antigen negative since the body has not yet mounted a response against the surface antigen, total anti-Hb core positive, and IgM anti-core positive. The presence of this last antibody, IgM anti-HBc, is important to test for because it and total anti-Hb core may be the only positive findings during the window period.

Immunity from vaccination

Incorrect. The serology is anti-Hb surface antigen positive, Hb surface antigen negative, and total anti-Hb core negative. The vaccine immunizes against HbS Ag. There is no anti-core Ag because the core is found in the virus but not the vaccine.

Vaccine and infection naive

Incorrect. This would be Hb surface Ag negative, anti-Hb surface antigen negative, and total anti-Hb core negative.

Summary