Epidemiology: criteria for causation: 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: criteria for causation

Sample item

While judging whether an observed association between an exposure and a disease is causal, which criterion among the Bradford Hill considerations is the only one that must always be satisfied?

ASpecificity of the associationBStrength of the associationCTemporality, with the exposure preceding the diseaseDBiological gradient (dose-response)

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

The answer and the reasoning

C. Temporality, with the exposure preceding the disease

A cause must precede its effect, so temporality is the one indispensable criterion. Strength, dose-response, consistency, plausibility and coherence support causation but are not required: weak associations can be causal, many causes have multiple effects, and some exposures show threshold effects. Specificity is the least useful, since smoking causes many diseases.

Option by option

A. Specificity of the association
Many causes produce several diseases, so specificity is not essential.
B. Strength of the association
A weak association can still be causal, so strength supports but is not essential.
C. Temporality, with the exposure preceding the disease (correct)
Correct. Without the exposure preceding the outcome, causation is impossible.
D. Biological gradient (dose-response)
Some causal exposures show threshold or no graded effects, so dose-response is supportive only.

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, Temporality, with the exposure preceding the disease. A cause must precede its effect, so temporality is the one indispensable criterion.

Why is "Specificity of the association" not the answer?

Many causes produce several diseases, so specificity is not essential.

Why is "Strength of the association" not the answer?

A weak association can still be causal, so strength supports but is not essential.

Why is "Biological gradient (dose-response)" not the answer?

Some causal exposures show threshold or no graded effects, so dose-response is supportive only.

What concept does this question test?

It tests Epidemiology: criteria for causation in PSM. Strength, dose-response, consistency, plausibility and coherence support causation but are not required: weak associations can be causal, many causes have multiple effects, and some exposures show threshold effects. Specificity is the least useful, since smoking causes many diseases.

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: criteria for causation?

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.