Screening: 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

Sample item

What happens to positive predictive value when disease prevalence increases, assuming test characteristics stay unchanged?

APositive predictive value becomes zeroBSpecificity necessarily becomes oneCPositive predictive value increasesDSensitivity necessarily decreases

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

The answer and the reasoning

C. Positive predictive value increases

When disease is more prevalent, a greater share of positive tests are true positives, increasing the positive predictive value of the same test.

Option by option

A. Positive predictive value becomes zero
Positive predictive value does not become zero with higher prevalence.
B. Specificity necessarily becomes one
Specificity does not automatically change with prevalence.
C. Positive predictive value increases (correct)
Correct: higher pretest probability increases the chance a positive is true.
D. Sensitivity necessarily decreases
Sensitivity is an intrinsic test characteristic in this assumption.

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.

Questions about this PSM question

What is the answer to this PSM question?

The best answer is C, Positive predictive value increases. When disease is more prevalent, a greater share of positive tests are true positives, increasing the positive predictive value of the same test.

Why is "Positive predictive value becomes zero" not the answer?

Positive predictive value does not become zero with higher prevalence.

Why is "Specificity necessarily becomes one" not the answer?

Specificity does not automatically change with prevalence.

Why is "Sensitivity necessarily decreases" not the answer?

Sensitivity is an intrinsic test characteristic in this assumption.

What concept does this question test?

It tests Screening in PSM. The correct option holds because: Correct: higher pretest probability increases the chance a positive is true.

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 Screening?

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.