Communicable diseases: slide falciparum 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 · Communicable diseases: slide falciparum rate

Sample item

In a block, 4,000 blood slides were examined in a year. 400 were positive for malaria parasites and 160 of these were Plasmodium falciparum. What is the slide falciparum rate?

A2 percentB40 percentC10 percentD4 percent

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

The answer and the reasoning

D. 4 percent

Slide falciparum rate is P. falciparum positive slides divided by slides examined, times 100: 160 by 4,000 is 4 percent. Slide positivity rate is all positive slides over slides examined, here 10 percent. Annual parasite incidence needs the population.

Option by option

A. 2 percent
Two percent has no basis in these numbers.
B. 40 percent
Forty percent is the proportion of positives that are falciparum, not the SFR.
C. 10 percent
Ten percent is the slide positivity rate, all species combined.
D. 4 percent (correct)
Correct. 160 divided by 4,000 gives 4 percent.

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 D, 4 percent. Slide falciparum rate is P.

Why is "2 percent" not the answer?

Two percent has no basis in these numbers.

Why is "40 percent" not the answer?

Forty percent is the proportion of positives that are falciparum, not the SFR.

Why is "10 percent" not the answer?

Ten percent is the slide positivity rate, all species combined.

What concept does this question test?

It tests Communicable diseases: slide falciparum rate in PSM. falciparum positive slides divided by slides examined, times 100: 160 by 4,000 is 4 percent. Slide positivity rate is all positive slides over slides examined, here 10 percent. Annual parasite incidence needs the 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 Communicable diseases: slide falciparum 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.