Communicable diseases: hepatitis B serology: practice question

A PSM question in the style of the NEET PG paper. Answer it first, then read why the right option is right and why each of the others is wrong.

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PSM · Communicable diseases: hepatitis B serology

Sample item

A 40-year-old nurse has the following results: HBsAg negative, total anti-HBc positive, anti-HBc IgM negative and anti-HBs positive at 120 mIU/mL. She has never been vaccinated. What is the correct interpretation?

Original practice item, not a recalled exam question. Nothing here is recorded.

The answer and the reasoning

B. Past resolved infection with natural immunity

Anti-HBs indicates immunity, and anti-HBc is made only after natural infection, not after vaccination. Negative HBsAg with positive anti-HBs and total anti-HBc, with negative IgM, means a past infection that has resolved. Vaccination alone gives anti-HBs without anti-HBc.

Option by option

  • A. Chronic hepatitis B carrier state

    A chronic carrier would remain HBsAg positive and would not have protective anti-HBs.

  • B. Past resolved infection with natural immunity (correct)

    Correct. Anti-HBc with anti-HBs and no HBsAg indicates a resolved natural infection.

  • C. Acute hepatitis B in the window period

    The window period has negative anti-HBs with positive anti-HBc IgM, which is not the case here.

  • D. Immunity due to vaccination only

    Vaccine-induced immunity produces anti-HBs without anti-HBc, so this pattern is not explained by vaccination, and she was never vaccinated.

Source note: Original NextPrep sample item — pending expert review. This item is original practice material awaiting independent expert review, so confirm important facts in a standard textbook.

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Questions about this PSM question

What is the answer to this PSM question?

The best answer is B, Past resolved infection with natural immunity. Anti-HBs indicates immunity, and anti-HBc is made only after natural infection, not after vaccination.

Why is "Chronic hepatitis B carrier state" not the answer?

A chronic carrier would remain HBsAg positive and would not have protective anti-HBs.

Why is "Acute hepatitis B in the window period" not the answer?

The window period has negative anti-HBs with positive anti-HBc IgM, which is not the case here.

Why is "Immunity due to vaccination only" not the answer?

Vaccine-induced immunity produces anti-HBs without anti-HBc, so this pattern is not explained by vaccination, and she was never vaccinated.

What concept does this question test?

It tests Communicable diseases: hepatitis B serology in PSM. Negative HBsAg with positive anti-HBs and total anti-HBc, with negative IgM, means a past infection that has resolved. Vaccination alone gives anti-HBs without anti-HBc.

How hard is this question?

We tag it as a multi-step question: it asks you to combine more than one idea. The tag is our own editorial judgement, not an official difficulty rating, so read the reason for every option, not only the answer.

How should I study Communicable diseases: hepatitis B serology?

Practise biostatistics with small calculations until sensitivity, predictive values and risk measures are automatic. Then use the flashcards and the other PSM questions on this site to test what stuck.

Is this a real NEET PG question?

No. It is an original practice item (editorial status: sample, version 1). NextPrep does not publish recalled or leaked questions, and independent faculty review of this item has not been completed yet, so confirm important facts in a standard textbook.