Communicable diseases: blood culture in typhoid: 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: blood culture in typhoid

Sample item

A 20-year-old with step-ladder fever for 5 days, relative bradycardia and abdominal discomfort is suspected to have enteric fever. Which investigation has the highest diagnostic yield at this stage?

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

The answer and the reasoning

D. Blood culture

Blood culture is positive in the majority of patients in the first week and remains the best single test early in the illness. Stool and urine cultures become more useful in the second and third weeks. A single Widal titre is unreliable in endemic areas because of baseline antibodies.

Option by option

  • A. Stool culture

    Stool culture is positive more often from the second or third week.

  • B. Widal test on a single serum sample

    A single Widal titre is unreliable in endemic regions because many people have background antibodies.

  • C. Urine culture

    Urine culture is positive less often and only later in the illness.

  • D. Blood culture (correct)

    Correct. Blood culture has the highest yield during the first week of illness.

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 PSM question

What is the answer to this PSM question?

The best answer is D, Blood culture. Blood culture is positive in the majority of patients in the first week and remains the best single test early in the illness.

Why is "Stool culture" not the answer?

Stool culture is positive more often from the second or third week.

Why is "Widal test on a single serum sample" not the answer?

A single Widal titre is unreliable in endemic regions because many people have background antibodies.

Why is "Urine culture" not the answer?

Urine culture is positive less often and only later in the illness.

What concept does this question test?

It tests Communicable diseases: blood culture in typhoid in PSM. Stool and urine cultures become more useful in the second and third weeks. A single Widal titre is unreliable in endemic areas because of baseline antibodies.

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: blood culture in typhoid?

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.