Serology: practice question

A Microbiology 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.

Try it

Microbiology · Serology

Sample item

A healthy health-care worker tests negative for HBsAg, positive for anti-HBs and negative for total anti-HBc. How is this best interpreted?

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

The answer and the reasoning

A. Immunity from hepatitis B vaccination

Vaccine contains only HBsAg, so it induces anti-HBs without anti-HBc. Natural infection stimulates antibodies against the core antigen as well, so anti-HBc would be positive after recovery.

Option by option

  • A. Immunity from hepatitis B vaccination (correct)

    Correct. Isolated anti-HBs reflects vaccine-induced immunity.

  • B. Acute infection in the window period

    In the window period HBsAg and anti-HBs are both negative, with IgM anti-HBc positive.

  • C. Immunity after past natural infection

    After natural recovery, anti-HBc would also be positive along with anti-HBs.

  • D. Chronic hepatitis B carrier state

    A carrier remains HBsAg positive, and anti-HBc would be present.

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.

More Microbiology questions

Questions about this Microbiology question

What is the answer to this Microbiology question?

The best answer is A, Immunity from hepatitis B vaccination. Vaccine contains only HBsAg, so it induces anti-HBs without anti-HBc.

Why is "Acute infection in the window period" not the answer?

In the window period HBsAg and anti-HBs are both negative, with IgM anti-HBc positive.

Why is "Immunity after past natural infection" not the answer?

After natural recovery, anti-HBc would also be positive along with anti-HBs.

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

A carrier remains HBsAg positive, and anti-HBc would be present.

What concept does this question test?

It tests Serology in Microbiology. Natural infection stimulates antibodies against the core antigen as well, so anti-HBc would be positive after recovery.

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 Serology?

Make a one-line identity card for each organism: shape and stain, defining test, toxin, disease and drug. Then use the flashcards and the other Microbiology 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.