Communicable diseases: typhoid carriers: 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: typhoid carriers

Sample item

A health officer wants to screen restaurant workers for chronic typhoid carriage in a town after repeated outbreaks. Which test is used for initial screening of suspected carriers, with confirmation by culture?

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

The answer and the reasoning

D. Vi antibody (Vi agglutination) test

Chronic carriers, who excrete Salmonella Typhi for more than a year (the gallbladder being the usual site), often have raised antibodies to the Vi antigen. A raised Vi titre is used to screen suspected carriers, and the diagnosis is confirmed by isolating the organism from stool, bile or duodenal aspirate. Widal tests indicate recent infection or vaccination and are poor for screening carriers.

Option by option

  • A. Widal test for H antibody

    H antibody persists after vaccination or past infection and has poor specificity for carriage.

  • B. Widal test for O antibody

    O antibody reflects recent or current infection and does not identify carriers.

  • C. Single blood culture

    Blood culture detects bacteraemia in acute illness, whereas carriers shed organisms in stool or bile.

  • D. Vi antibody (Vi agglutination) test (correct)

    Correct. Raised Vi antibody identifies likely carriers who then need culture confirmation.

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 D, Vi antibody (Vi agglutination) test. Chronic carriers, who excrete Salmonella Typhi for more than a year (the gallbladder being the usual site), often have raised antibodies to the Vi antigen.

Why is "Widal test for H antibody" not the answer?

H antibody persists after vaccination or past infection and has poor specificity for carriage.

Why is "Widal test for O antibody" not the answer?

O antibody reflects recent or current infection and does not identify carriers.

Why is "Single blood culture" not the answer?

Blood culture detects bacteraemia in acute illness, whereas carriers shed organisms in stool or bile.

What concept does this question test?

It tests Communicable diseases: typhoid carriers in PSM. A raised Vi titre is used to screen suspected carriers, and the diagnosis is confirmed by isolating the organism from stool, bile or duodenal aspirate. Widal tests indicate recent infection or vaccination and are poor for screening carriers.

How hard is this question?

We tag it as an application question: it asks you to use a fact on a patient or a finding. 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: typhoid carriers?

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.