Bone infection: CBNAAT in skeletal tuberculosis: practice question

A Orthopaedics 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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Orthopaedics · Bone infection: CBNAAT in skeletal tuberculosis

Sample item

Pus aspirated from a cold abscess in a patient with suspected spinal tuberculosis is sent for CBNAAT. What additional information does this test give besides detecting Mycobacterium tuberculosis?

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

The answer and the reasoning

C. Rifampicin resistance

CBNAAT (Xpert MTB/RIF) is a PCR-based test that detects M. tuberculosis DNA and, through the rpoB gene, rifampicin resistance. Results are available in about two hours. It is useful on pus, tissue and synovial fluid in skeletal TB, where smears are often negative.

Option by option

  • A. Isoniazid dose

    The test does not guide isoniazid dosing.

  • B. Duration of therapy

    It cannot determine the duration of therapy.

  • C. Rifampicin resistance (correct)

    Correct. CBNAAT detects rifampicin resistance through the rpoB gene.

  • D. Atypical mycobacteria species

    It does not speciate atypical mycobacteria.

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 Orthopaedics question

What is the answer to this Orthopaedics question?

The best answer is C, Rifampicin resistance. CBNAAT (Xpert MTB/RIF) is a PCR-based test that detects M.

Why is "Isoniazid dose" not the answer?

The test does not guide isoniazid dosing.

Why is "Duration of therapy" not the answer?

It cannot determine the duration of therapy.

Why is "Atypical mycobacteria species" not the answer?

It does not speciate atypical mycobacteria.

What concept does this question test?

It tests Bone infection: CBNAAT in skeletal tuberculosis in Orthopaedics. tuberculosis DNA and, through the rpoB gene, rifampicin resistance. Results are available in about two hours. It is useful on pus, tissue and synovial fluid in skeletal TB, where smears are often negative.

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 Bone infection: CBNAAT in skeletal tuberculosis?

Pair each fracture with its classic complication and nerve injured. Then use the flashcards and the other Orthopaedics 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.