Chemotherapy: abacavir hypersensitivity: practice question

A Pharmacology 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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Pharmacology · Chemotherapy: abacavir hypersensitivity

Sample item

A man with HIV starts an abacavir-containing regimen. On day 10 he has fever, rash, vomiting, malaise and cough. Which pre-treatment screening test could have prevented this?

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

The answer and the reasoning

C. HLA-B*57:01

Abacavir hypersensitivity is strongly associated with HLA-B*57:01, and screening before starting reduces the risk. Once it occurs, the drug is stopped permanently and never rechallenged, because rechallenge can cause fatal reactions. This is why abacavir is used only after a negative test.

Option by option

  • A. Thiopurine methyltransferase activity

    TPMT activity predicts thiopurine toxicity.

  • B. HLA-B*58:01

    HLA-B*58:01 predicts allopurinol hypersensitivity.

  • C. HLA-B*57:01 (correct)

    Correct. A negative test makes hypersensitivity very unlikely.

  • D. HLA-B*15:02

    HLA-B*15:02 predicts carbamazepine-induced Stevens-Johnson syndrome.

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 Pharmacology question

What is the answer to this Pharmacology question?

The best answer is C, HLA-B*57:01. Abacavir hypersensitivity is strongly associated with HLA-B*57:01, and screening before starting reduces the risk.

Why is "Thiopurine methyltransferase activity" not the answer?

TPMT activity predicts thiopurine toxicity.

Why is "HLA-B*58:01" not the answer?

HLA-B*58:01 predicts allopurinol hypersensitivity.

Why is "HLA-B*15:02" not the answer?

HLA-B*15:02 predicts carbamazepine-induced Stevens-Johnson syndrome.

What concept does this question test?

It tests Chemotherapy: abacavir hypersensitivity in Pharmacology. Once it occurs, the drug is stopped permanently and never rechallenged, because rechallenge can cause fatal reactions. This is why abacavir is used only after a negative test.

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 Chemotherapy: abacavir hypersensitivity?

Learn drugs as classes, then the exception in each class that an examiner would pick. Then use the flashcards and the other Pharmacology 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.