Virology: acute HIV and fourth-generation assay: 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.

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Microbiology · Virology: acute HIV and fourth-generation assay

Sample item

A 29-year-old man develops fever, rash and pharyngitis 10 days after unprotected sex. A fourth-generation HIV antigen and antibody test is reactive, but the HIV-1/HIV-2 antibody differentiation assay is non-reactive. What is the best next step to confirm the diagnosis?

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

The answer and the reasoning

C. HIV-1 RNA by nucleic acid testing

In the first weeks of infection, p24 antigen and viral RNA appear before antibodies. A fourth-generation test can therefore be reactive from detection of p24 while antibody-based confirmatory tests are still negative or indeterminate. HIV-1 RNA testing confirms acute infection.

Option by option

  • A. Start antiretroviral therapy with no further testing

    Treatment decisions should follow a confirmed diagnosis, and a reactive screening test alone has false-positive possibilities.

  • B. Western blot immediately

    Western blot detects antibody and would be negative or indeterminate this early.

  • C. HIV-1 RNA by nucleic acid testing (correct)

    Viral RNA is detectable before antibody and settles the diagnosis in acute infection.

  • D. CD4 lymphocyte count

    CD4 count assesses immune status and does not confirm infection.

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 C, HIV-1 RNA by nucleic acid testing. In the first weeks of infection, p24 antigen and viral RNA appear before antibodies.

Why is "Start antiretroviral therapy with no further testing" not the answer?

Treatment decisions should follow a confirmed diagnosis, and a reactive screening test alone has false-positive possibilities.

Why is "Western blot immediately" not the answer?

Western blot detects antibody and would be negative or indeterminate this early.

Why is "CD4 lymphocyte count" not the answer?

CD4 count assesses immune status and does not confirm infection.

What concept does this question test?

It tests Virology: acute HIV and fourth-generation assay in Microbiology. A fourth-generation test can therefore be reactive from detection of p24 while antibody-based confirmatory tests are still negative or indeterminate. HIV-1 RNA testing confirms acute infection.

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 Virology: acute HIV and fourth-generation assay?

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.