Communicable diseases: dengue testing in late febrile phase: 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.

Try it

PSM · Communicable diseases: dengue testing in late febrile phase

Sample item

A patient presents on day 7 of a febrile illness with suspected dengue, and the NS1 antigen test is negative. Which test is most appropriate?

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

The answer and the reasoning

B. IgM antibody capture ELISA

NS1 antigenaemia and viraemia fade by about day 5, so by day 7 an IgM antibody capture ELISA is the appropriate test. Virus isolation and PCR also work best early. Repeating NS1 would add little.

Option by option

  • A. Repeat NS1 antigen

    NS1 antigen declines after the first five days, so a repeat would likely stay negative.

  • B. IgM antibody capture ELISA (correct)

    Correct. IgM antibodies are detectable from about day 5.

  • C. RT-PCR on blood

    RT-PCR is most sensitive early in the illness while viraemia lasts.

  • D. Virus isolation in cell culture

    Virus isolation is a research test, slow and best in early viraemia.

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 PSM questions

Questions about this PSM question

What is the answer to this PSM question?

The best answer is B, IgM antibody capture ELISA. NS1 antigenaemia and viraemia fade by about day 5, so by day 7 an IgM antibody capture ELISA is the appropriate test.

Why is "Repeat NS1 antigen" not the answer?

NS1 antigen declines after the first five days, so a repeat would likely stay negative.

Why is "RT-PCR on blood" not the answer?

RT-PCR is most sensitive early in the illness while viraemia lasts.

Why is "Virus isolation in cell culture" not the answer?

Virus isolation is a research test, slow and best in early viraemia.

What concept does this question test?

It tests Communicable diseases: dengue testing in late febrile phase in PSM. Virus isolation and PCR also work best early. Repeating NS1 would add little.

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: dengue testing in late febrile phase?

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.