Epidemiology: 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.

Try it

PSM · Epidemiology

Sample item

In a stable population, the incidence of a chronic disease is 10 per 1000 per year and the average duration is 5 years. What is the approximate prevalence?

A50 per 1000B15 per 1000C2 per 1000D100 per 1000

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

The answer and the reasoning

A. 50 per 1000

In a steady state, prevalence is approximately incidence multiplied by mean duration. Here it is 10 per 1000 per year times 5 years, which is 50 per 1000. Improved treatment that prolongs survival increases prevalence without changing incidence.

Option by option

A. 50 per 1000 (correct)
Correct. Prevalence equals incidence multiplied by duration.
B. 15 per 1000
15 per 1000 adds the two values, which has no meaning.
C. 2 per 1000
2 per 1000 divides instead of multiplies.
D. 100 per 1000
100 per 1000 doubles the correct result without basis.

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 A, 50 per 1000. In a steady state, prevalence is approximately incidence multiplied by mean duration.

Why is "15 per 1000" not the answer?

15 per 1000 adds the two values, which has no meaning.

Why is "2 per 1000" not the answer?

2 per 1000 divides instead of multiplies.

Why is "100 per 1000" not the answer?

100 per 1000 doubles the correct result without basis.

What concept does this question test?

It tests Epidemiology in PSM. Here it is 10 per 1000 per year times 5 years, which is 50 per 1000. Improved treatment that prolongs survival increases prevalence without changing incidence.

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?

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.