Epidemiology: case fatality rate: 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: case fatality rate

Sample item

A village of 2,000 people has an outbreak of diphtheria in which 80 persons fall ill and 6 of them die. What is the case fatality rate?

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

The answer and the reasoning

C. 7.5%

Case fatality rate is the number of deaths from a disease divided by the number of diagnosed cases of that disease, expressed as a percentage. Here it is 6 / 80 x 100 = 7.5%. It reflects the killing power of the disease and is a measure of severity, not of risk in the whole population.

Option by option

  • A. 13.3%

    This is 80 / 6, the number of cases per death, which inverts the ratio.

  • B. 4%

    This is the attack rate (80 / 2,000), which measures how many in the population became ill.

  • C. 7.5% (correct)

    Correct. Deaths (6) divided by cases (80) gives 0.075, or 7.5%.

  • D. 0.3%

    This is the cause-specific death rate in the whole population (6 / 2,000), which uses the wrong denominator.

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, 7.5%. Case fatality rate is the number of deaths from a disease divided by the number of diagnosed cases of that disease, expressed as a percentage.

Why is "13.3%" not the answer?

This is 80 / 6, the number of cases per death, which inverts the ratio.

Why is "4%" not the answer?

This is the attack rate (80 / 2,000), which measures how many in the population became ill.

Why is "0.3%" not the answer?

This is the cause-specific death rate in the whole population (6 / 2,000), which uses the wrong denominator.

What concept does this question test?

It tests Epidemiology: case fatality rate in PSM. Here it is 6 / 80 x 100 = 7.5%. It reflects the killing power of the disease and is a measure of severity, not of risk in the whole population.

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: case fatality rate?

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.