Epidemiology: SnNout: 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 · Epidemiology: SnNout

Sample item

A rapid test for a disease has a sensitivity of 98%. A patient with symptoms of the disease tests negative. What is the most reasonable conclusion?

AA false positive is the most likely explanationBThe disease can be largely ruled outCThe result says nothing without the prevalenceDThe disease is confirmed despite the result

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

The answer and the reasoning

B. The disease can be largely ruled out

A highly sensitive test misses very few true cases, so a negative result makes the disease unlikely, summarised as SnNout. A highly specific test, when positive, helps rule the disease in. The predictive value still varies with prevalence, but with 98% sensitivity a negative result rarely hides disease.

Option by option

A. A false positive is the most likely explanation
A false positive cannot occur when the test result is negative.
B. The disease can be largely ruled out (correct)
Correct. With so few false negatives, a negative result largely excludes disease.
C. The result says nothing without the prevalence
Prevalence affects predictive values, but high sensitivity already makes a negative result informative.
D. The disease is confirmed despite the result
A negative result cannot confirm a disease.

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 B, The disease can be largely ruled out. A highly sensitive test misses very few true cases, so a negative result makes the disease unlikely, summarised as SnNout.

Why is "A false positive is the most likely explanation" not the answer?

A false positive cannot occur when the test result is negative.

Why is "The result says nothing without the prevalence" not the answer?

Prevalence affects predictive values, but high sensitivity already makes a negative result informative.

Why is "The disease is confirmed despite the result" not the answer?

A negative result cannot confirm a disease.

What concept does this question test?

It tests Epidemiology: SnNout in PSM. A highly specific test, when positive, helps rule the disease in. The predictive value still varies with prevalence, but with 98% sensitivity a negative result rarely hides 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 Epidemiology: SnNout?

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.