Respiratory medicine: Light criteria: 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: Light criteria

Sample item

Pleural fluid protein is 4.2 g/dL with serum protein 6.0 g/dL, and fluid LDH is 280 U/L with serum LDH 400 U/L (upper limit of normal 300). Interpretation?

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

The answer and the reasoning

A. Exudate, because the pleural to serum protein ratio exceeds 0.5

Light criteria define an exudate if any one is met: pleural to serum protein ratio above 0.5, LDH ratio above 0.6, or pleural LDH above two-thirds of the upper normal serum limit. The protein ratio here is 0.7. Hence the fluid is an exudate.

Option by option

  • A. Exudate, because the pleural to serum protein ratio exceeds 0.5 (correct)

    Correct. A protein ratio of 0.7 meets exudate criteria.

  • B. Transudate, since LDH is below normal serum limit

    Meeting any one criterion is enough, so exudate is diagnosed.

  • C. Cannot be classified

    The values permit classification.

  • D. Chylous effusion

    Chylous effusion is defined by triglycerides, not protein ratio.

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, Exudate, because the pleural to serum protein ratio exceeds 0.5. Light criteria define an exudate if any one is met: pleural to serum protein ratio above 0.

Why is "Transudate, since LDH is below normal serum limit" not the answer?

Meeting any one criterion is enough, so exudate is diagnosed.

Why is "Cannot be classified" not the answer?

The values permit classification.

Why is "Chylous effusion" not the answer?

Chylous effusion is defined by triglycerides, not protein ratio.

What concept does this question test?

It tests Respiratory medicine: Light criteria in General Medicine. 5, LDH ratio above 0.6, or pleural LDH above two-thirds of the upper normal serum limit. The protein ratio here is 0.7. Hence the fluid is an exudate.

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: Light criteria?

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.