Epidemiology: biological gradient: 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: biological gradient

Sample item

A cohort study finds the relative risk of lung cancer to be 1 in non-smokers, 4 in those smoking fewer than 10 cigarettes a day, 9 in those smoking 10 to 20, and 16 in those smoking more than 20. Which causal criterion does this pattern support?

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

The answer and the reasoning

C. Dose-response relationship

A rising risk with increasing exposure is a dose-response or biological gradient relationship and strengthens the case for causation. Temporality needs exposure to precede the disease, which is not shown by a gradient. Specificity means one cause leading to one effect.

Option by option

  • A. Experimental evidence

    Experimental evidence would need a trial or removal of the exposure, not graded cohort data.

  • B. Temporality

    Temporality concerns the order of exposure and outcome, not the amount of exposure.

  • C. Dose-response relationship (correct)

    Correct. Risk increasing step by step with the amount of exposure is a dose-response relationship.

  • D. Specificity

    Specificity is a one-to-one relation between cause and effect, which tobacco does not have.

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, Dose-response relationship. A rising risk with increasing exposure is a dose-response or biological gradient relationship and strengthens the case for causation.

Why is "Experimental evidence" not the answer?

Experimental evidence would need a trial or removal of the exposure, not graded cohort data.

Why is "Temporality" not the answer?

Temporality concerns the order of exposure and outcome, not the amount of exposure.

Why is "Specificity" not the answer?

Specificity is a one-to-one relation between cause and effect, which tobacco does not have.

What concept does this question test?

It tests Epidemiology: biological gradient in PSM. Temporality needs exposure to precede the disease, which is not shown by a gradient. Specificity means one cause leading to one effect.

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: biological gradient?

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.