Virology: HIV early infant diagnosis: 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: HIV early infant diagnosis

Sample item

A 6-week-old exclusively breast-fed infant is born to an HIV-positive mother. Which test is most appropriate to find out whether the infant is infected?

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

The answer and the reasoning

A. HIV-1 DNA PCR on a dried blood spot

Maternal IgG crosses the placenta and persists in the infant for up to 18 months, so antibody tests cannot separate infected from exposed infants early in life. Virological testing for proviral DNA or RNA is therefore used for early infant diagnosis, and in India it is done on dried blood spots from 6 weeks. A positive result is confirmed with a second sample.

Option by option

  • A. HIV-1 DNA PCR on a dried blood spot (correct)

    Correct. Virological testing detects the virus itself and is not confounded by maternal antibody.

  • B. Rapid HIV antibody test on the infant's blood

    An antibody test would be positive from passively acquired maternal IgG.

  • C. Repeat ELISA for antibody at 6 weeks

    ELISA is also an antibody test and has the same limitation.

  • D. CD4 count of the infant

    CD4 count is for staging and does not diagnose 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.

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Questions about this Microbiology question

What is the answer to this Microbiology question?

The best answer is A, HIV-1 DNA PCR on a dried blood spot. Maternal IgG crosses the placenta and persists in the infant for up to 18 months, so antibody tests cannot separate infected from exposed infants early in life.

Why is "Rapid HIV antibody test on the infant's blood" not the answer?

An antibody test would be positive from passively acquired maternal IgG.

Why is "Repeat ELISA for antibody at 6 weeks" not the answer?

ELISA is also an antibody test and has the same limitation.

Why is "CD4 count of the infant" not the answer?

CD4 count is for staging and does not diagnose infection.

What concept does this question test?

It tests Virology: HIV early infant diagnosis in Microbiology. Virological testing for proviral DNA or RNA is therefore used for early infant diagnosis, and in India it is done on dried blood spots from 6 weeks. A positive result is confirmed with a second sample.

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: HIV early infant diagnosis?

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.