Communicable diseases: diagnosis of enterobiasis: 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: diagnosis of enterobiasis

Sample item

A 5-year-old child has disturbed sleep and intense perianal itching at night. Repeated routine stool microscopy is negative. What is the most suitable investigation?

ACellophane tape swab from the perianal skin in the morningBString test for larvaeCDuodenal aspirate examinationDStool culture on selective media

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

The answer and the reasoning

A. Cellophane tape swab from the perianal skin in the morning

Female Enterobius worms lay eggs on the perianal skin at night, so stool examination often misses them. The sticky cellophane tape (NIH) swab taken before washing in the morning picks up eggs for microscopy. All family members should be treated and hygiene improved.

Option by option

A. Cellophane tape swab from the perianal skin in the morning (correct)
Correct. Eggs are deposited on the perianal skin, so a morning tape swab is the test of choice.
B. String test for larvae
The string test is used to look for Giardia trophozoites or Strongyloides larvae.
C. Duodenal aspirate examination
Duodenal aspirate is used for Giardia or Strongyloides, not for pinworm.
D. Stool culture on selective media
Culture on selective media is used for bacterial enteric pathogens, not for pinworm.

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, Cellophane tape swab from the perianal skin in the morning. Female Enterobius worms lay eggs on the perianal skin at night, so stool examination often misses them.

Why is "String test for larvae" not the answer?

The string test is used to look for Giardia trophozoites or Strongyloides larvae.

Why is "Duodenal aspirate examination" not the answer?

Duodenal aspirate is used for Giardia or Strongyloides, not for pinworm.

Why is "Stool culture on selective media" not the answer?

Culture on selective media is used for bacterial enteric pathogens, not for pinworm.

What concept does this question test?

It tests Communicable diseases: diagnosis of enterobiasis in PSM. The sticky cellophane tape (NIH) swab taken before washing in the morning picks up eggs for microscopy. All family members should be treated and hygiene improved.

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: diagnosis of enterobiasis?

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.