Screening: positive predictive value: 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 · Screening: positive predictive value

Sample item

When disease prevalence falls while sensitivity and specificity remain unchanged, what usually happens to the positive predictive value of a screening test?

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

The answer and the reasoning

C. It decreases

Positive predictive value depends on disease prevalence as well as test performance. With rarer disease, a greater proportion of positive results are false positives, reducing PPV.

Option by option

  • A. It becomes equal to sensitivity

    Sensitivity and PPV are distinct measures.

  • B. It remains fixed

    PPV is not fixed because prevalence changes it.

  • C. It decreases (correct)

    Correct. Lower prevalence generally lowers the probability that a positive result is a true positive.

  • D. It increases markedly

    Higher PPV is more likely when prevalence rises.

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 C, It decreases. Positive predictive value depends on disease prevalence as well as test performance.

Why is "It becomes equal to sensitivity" not the answer?

Sensitivity and PPV are distinct measures.

Why is "It remains fixed" not the answer?

PPV is not fixed because prevalence changes it.

Why is "It increases markedly" not the answer?

Higher PPV is more likely when prevalence rises.

What concept does this question test?

It tests Screening: positive predictive value in PSM. With rarer disease, a greater proportion of positive results are false positives, reducing PPV.

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 Screening: positive predictive value?

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.