Stool examination: Kato-Katz egg count: practice question

A Microbiology 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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Microbiology · Stool examination: Kato-Katz egg count

Sample item

A school survey uses the Kato-Katz method with the standard 41.7 mg template. A smear shows 12 Ascaris lumbricoides eggs. Using the usual multiplication factor, what is the approximate egg count and WHO intensity class?

AAbout 500 eggs per gram, light infectionBAbout 12,000 eggs per gram, moderate infectionCAbout 288 eggs per gram, light infectionDAbout 12 eggs per gram, light infection

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

The answer and the reasoning

C. About 288 eggs per gram, light infection

The Kato-Katz method converts eggs counted on a fixed-volume smear into eggs per gram. The standard 41.7 mg template delivers about 1/24 of a gram, so the factor is 24 and 12 eggs correspond to about 288 per gram. For Ascaris, WHO classes 1 to 4,999 eggs per gram as light infection and 5,000 to 49,999 as moderate.

Option by option

A. About 500 eggs per gram, light infection
A factor of 41.7 is not the multiplier for the standard 41.7 mg template; it confuses the template weight with the factor.
B. About 12,000 eggs per gram, moderate infection
Multiplying by 1,000 ignores the fixed template volume, and 12,000 would not follow from 12 eggs on one smear.
C. About 288 eggs per gram, light infection (correct)
Correct. 12 multiplied by 24 is 288 eggs per gram, which is below 5,000 and so light.
D. About 12 eggs per gram, light infection
The raw count on the smear is not the number per gram; it must be multiplied by the template factor.

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 Microbiology question

What is the answer to this Microbiology question?

The best answer is C, About 288 eggs per gram, light infection. The Kato-Katz method converts eggs counted on a fixed-volume smear into eggs per gram.

Why is "About 500 eggs per gram, light infection" not the answer?

A factor of 41.7 is not the multiplier for the standard 41.7 mg template; it confuses the template weight with the factor.

Why is "About 12,000 eggs per gram, moderate infection" not the answer?

Multiplying by 1,000 ignores the fixed template volume, and 12,000 would not follow from 12 eggs on one smear.

Why is "About 12 eggs per gram, light infection" not the answer?

The raw count on the smear is not the number per gram; it must be multiplied by the template factor.

What concept does this question test?

It tests Stool examination: Kato-Katz egg count in Microbiology. The standard 41.7 mg template delivers about 1/24 of a gram, so the factor is 24 and 12 eggs correspond to about 288 per gram. For Ascaris, WHO classes 1 to 4,999 eggs per gram as light infection and 5,000 to 49,999 as moderate.

How hard is this question?

We tag it as a multi-step question: it asks you to combine more than one idea. 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 Stool examination: Kato-Katz egg count?

Make a one-line identity card for each organism: shape and stain, defining test, toxin, disease and drug. Then use the flashcards and the other Microbiology 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.