Respiratory medicine: pleural fluid classification: 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.

Try it

General Medicine · Respiratory medicine: pleural fluid classification

Sample item

A 66-year-old man on furosemide for chronic heart failure has bilateral pleural effusions. Pleural fluid protein is 3.0 g/dL (serum 6.8 g/dL) and pleural LDH is 260 IU/L (serum LDH 200 IU/L, upper limit of normal for serum 220 IU/L). Serum albumin is 3.9 g/dL and pleural fluid albumin is 2.3 g/dL. What is the best interpretation?

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

The answer and the reasoning

A. Transudate from heart failure; diuresis has concentrated the fluid, and the albumin gradient of 1.6 g/dL reclassifies it

Light's criteria label fluid an exudate if the protein ratio is above 0.5, the LDH ratio above 0.6, or pleural LDH above two-thirds of the serum upper limit; here only the LDH criteria are met (ratio 1.3, and 260 exceeds 147). Diuretics can concentrate pleural protein and LDH and misclassify cardiac transudates. The serum minus pleural albumin gradient above 1.2 g/dL (3.9 minus 2.3 = 1.6) indicates a transudate.

Option by option

  • A. Transudate from heart failure; diuresis has concentrated the fluid, and the albumin gradient of 1.6 g/dL reclassifies it (correct)

    Correct. The gradient above 1.2 g/dL identifies a diuretic-affected cardiac transudate that Light's criteria misclassify.

  • B. Parapneumonic exudate needing urgent intercostal drainage

    A parapneumonic effusion needs fever, consolidation and typically low pH or glucose; it is not suggested by bilateral effusions in heart failure.

  • C. Exudate from tuberculosis, so empirical antituberculosis therapy is indicated

    Tuberculous effusion is lymphocytic with high ADA and a high protein ratio, and nothing here supports it.

  • D. Exudate, because it meets an LDH criterion, so thoracoscopic pleural biopsy is needed

    Meeting one LDH criterion misclassifies diuresed cardiac effusions; the protein ratio is 0.44 and the albumin gradient shows a transudate.

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.

More General Medicine questions

Questions about this General Medicine question

What is the answer to this General Medicine question?

The best answer is A, Transudate from heart failure; diuresis has concentrated the fluid, and the albumin gradient of 1.6 g/dL reclassifies it. Light's criteria label fluid an exudate if the protein ratio is above 0.

Why is "Parapneumonic exudate needing urgent intercostal drainage" not the answer?

A parapneumonic effusion needs fever, consolidation and typically low pH or glucose; it is not suggested by bilateral effusions in heart failure.

Why is "Exudate from tuberculosis, so empirical antituberculosis therapy is i…" not the answer?

Tuberculous effusion is lymphocytic with high ADA and a high protein ratio, and nothing here supports it.

Why is "Exudate, because it meets an LDH criterion, so thoracoscopic pleural…" not the answer?

Meeting one LDH criterion misclassifies diuresed cardiac effusions; the protein ratio is 0.44 and the albumin gradient shows a transudate.

What concept does this question test?

It tests Respiratory medicine: pleural fluid classification in General Medicine. 5, the LDH ratio above 0.6, or pleural LDH above two-thirds of the serum upper limit; here only the LDH criteria are met (ratio 1.3, and 260 exceeds 147). Diuretics can concentrate pleural protein and LDH and misclassify cardiac transudates. The serum minus pleural albumin gradient above 1.2 g/dL (3.9 minus 2.3 = 1.6) indicates a transudate.

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: pleural fluid classification?

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.