Respiratory medicine: DLCO: 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: DLCO

Sample item

Which condition increases the diffusing capacity for carbon monoxide?

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

The answer and the reasoning

A. Pulmonary haemorrhage as in Goodpasture syndrome

DLCO is reduced in emphysema, fibrosis, pulmonary vascular disease and anaemia, but is raised by alveolar haemorrhage because haemoglobin in the airspaces binds carbon monoxide. Polycythaemia, left-to-right shunts and asthma may also raise it.

Option by option

  • A. Pulmonary haemorrhage as in Goodpasture syndrome (correct)

    Correct. Intra-alveolar blood binds CO and raises DLCO.

  • B. Pulmonary fibrosis

    Fibrosis thickens the membrane and lowers DLCO.

  • C. Anaemia

    Anaemia lowers DLCO.

  • D. Emphysema

    Emphysema destroys the membrane and lowers DLCO.

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 General Medicine question

What is the answer to this General Medicine question?

The best answer is A, Pulmonary haemorrhage as in Goodpasture syndrome. DLCO is reduced in emphysema, fibrosis, pulmonary vascular disease and anaemia, but is raised by alveolar haemorrhage because haemoglobin in the airspaces binds carbon monoxide.

Why is "Pulmonary fibrosis" not the answer?

Fibrosis thickens the membrane and lowers DLCO.

Why is "Anaemia" not the answer?

Anaemia lowers DLCO.

Why is "Emphysema" not the answer?

Emphysema destroys the membrane and lowers DLCO.

What concept does this question test?

It tests Respiratory medicine: DLCO in General Medicine. Polycythaemia, left-to-right shunts and asthma may also raise it.

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 Respiratory medicine: DLCO?

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.