Virology Practice Question

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?

Answer Choices

Immunity from previous infection
Chronic infection
Acute infection
Immunity from vaccination
Vaccine and infection naive

Show Answer and Explanations

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

Summary: Immunity against Hepatitis B from prior exposure: anti-Hb surface antibody (anti-HbS) positive, Hb surface antigen negative, and total anti-Hb core positive.