Respiratory medicine: methacholine challenge: practice question

A General Medicine 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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General Medicine · Respiratory medicine: methacholine challenge

Sample item

A 25-year-old has episodic nocturnal cough, but spirometry and bronchodilator response are normal between episodes. A methacholine challenge is performed. Which result supports a diagnosis of asthma?

AFEV1 falls by 5% at the highest doseBFEV1 rises by 12% after the challengeCFVC rises with no change in FEV1DFEV1 falls by 20% at a low methacholine dose

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

The answer and the reasoning

D. FEV1 falls by 20% at a low methacholine dose

A methacholine challenge detects airway hyperresponsiveness. A fall in FEV1 of 20% at a low dose (a low PC20) supports asthma, whereas a negative test has a high negative predictive value and makes asthma unlikely.

Option by option

A. FEV1 falls by 5% at the highest dose
A small fall at the highest dose is a negative result, as normal airways respond only at high doses.
B. FEV1 rises by 12% after the challenge
A rise in FEV1 is the response to a bronchodilator and not to methacholine.
C. FVC rises with no change in FEV1
A rise in FVC with stable FEV1 is not a bronchoprovocation result.
D. FEV1 falls by 20% at a low methacholine dose (correct)
Correct. Bronchoconstriction at a low dose shows airway hyperresponsiveness.

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 General Medicine question

What is the answer to this General Medicine question?

The best answer is D, FEV1 falls by 20% at a low methacholine dose. A methacholine challenge detects airway hyperresponsiveness.

Why is "FEV1 falls by 5% at the highest dose" not the answer?

A small fall at the highest dose is a negative result, as normal airways respond only at high doses.

Why is "FEV1 rises by 12% after the challenge" not the answer?

A rise in FEV1 is the response to a bronchodilator and not to methacholine.

Why is "FVC rises with no change in FEV1" not the answer?

A rise in FVC with stable FEV1 is not a bronchoprovocation result.

What concept does this question test?

It tests Respiratory medicine: methacholine challenge in General Medicine. A fall in FEV1 of 20% at a low dose (a low PC20) supports asthma, whereas a negative test has a high negative predictive value and makes asthma unlikely.

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 Respiratory medicine: methacholine challenge?

For each disease know the classic presentation, the best test, and the first-line treatment. Then use the flashcards and the other General Medicine 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.