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Azathioprine safety — SCE Rheumatology MCQ

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HardRheumatological PharmacologyAzathioprine safetySCE Rheumatology

A 35-year-old woman with SLE is being considered for azathioprine as a steroid-sparing agent. FBC, LFTs and renal function are normal. She has never taken thiopurines. The clinician wants to reduce the risk of severe early myelotoxicity. What is the most appropriate investigation?

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Correct answer: B — TPMT activity or genotype testing

The best answer is “TPMT activity or genotype testing”. TPMT activity or genotype testing most directly resolves the diagnostic or staging uncertainty at this point in the pathway; the other investigations answer different questions or have lower yield. The remaining choices—“HLA-B27 testing, with clinical reassessment”, “Schirmer test, after safety review”, “Serum urate, after specialist assessment”, “Anti-CCP antibody, with clinical reassessment”—are credible in related rheumatology presentations, but each addresses a different diagnosis, investigation, treatment sequence or complication and does not fit the decisive findings in this stem.

Reference: NICE NG100 rheumatoid arthritis in adults: https://www.nice.org.uk/guidance/ng100/chapter/Recommendations