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Serum Tryptase Anaphylaxis Investigation — FRCA Final MCQ

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ModerateGeneral AnaesthesiaSerum Tryptase Anaphylaxis InvestigationFRCA Final

A 45-year-old woman develops anaphylaxis during GA. After IM adrenaline 500 mcg and IV fluid resuscitation, she stabilises. What blood test should be taken at specific time points to confirm the diagnosis retrospectively?

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Correct answer: D — IgE levels at 1 and 4 hours

Serial serum tryptase: taken at 1h, 4h (or as close to 6h as possible), and >24h post-reaction (baseline). Tryptase is released from mast cells during anaphylaxis with a peak at 1-2h. A rise >20% above baseline + above 2 + (1.2 × baseline) confirms mast cell degranulation. Elevated tryptase supports anaphylaxis diagnosis and triggers allergy clinic referral.

Reference: RCUK/RCoA – 2024 – Perioperative anaphylaxis investigation; NICE – 2020 – Anaphylaxis