Screening tests: 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 tests

Sample item

What is the specificity of a diagnostic test?

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

The answer and the reasoning

C. Probability that the test is negative when disease is absent

Specificity is the ability of a test to correctly identify people without disease, calculated as true negatives divided by all nondiseased people; high specificity reduces false positives.

Option by option

  • A. Probability of recovery after treatment

    Recovery after treatment measures outcome, not test specificity.

  • B. Proportion of exposed people becoming ill

    Illness among exposed people is an attack or risk measure.

  • C. Probability that the test is negative when disease is absent (correct)

    Correct: specificity is the true-negative rate in people without disease.

  • D. Probability that the test is positive when disease is present

    The true-positive rate in disease is sensitivity.

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 C, Probability that the test is negative when disease is absent. Specificity is the ability of a test to correctly identify people without disease, calculated as true negatives divided by all nondiseased people; high specificity reduces false positives.

Why is "Probability of recovery after treatment" not the answer?

Recovery after treatment measures outcome, not test specificity.

Why is "Proportion of exposed people becoming ill" not the answer?

Illness among exposed people is an attack or risk measure.

Why is "Probability that the test is positive when disease is present" not the answer?

The true-positive rate in disease is sensitivity.

What concept does this question test?

It tests Screening tests in PSM. The correct option holds because: Correct: specificity is the true-negative rate in people without disease.

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 tests?

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.