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Mast Cell Tryptase Sampling — FRCA Final MCQ

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ModeratePreoperative AssessmentMast Cell Tryptase SamplingFRCA Final

A 50-year-old man has a suspected anaphylaxis to rocuronium during induction of anaesthesia. The reaction is treated successfully. A serum mast cell tryptase is taken at 1 hour post-reaction. According to current guidelines, what is the recommended sampling schedule for mast cell tryptase?

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Correct answer: E — Three samples: at time of reaction, 1-2 hours after onset, and >24 hours (baseline)

The Resuscitation Council UK and Association of Anaesthetists recommend three mast cell tryptase samples: (1) as soon as possible after treatment has started (not delaying treatment), (2) 1-2 hours after symptom onset (peak level), and (3) >24 hours after the event or at follow-up (baseline). Comparing acute levels to the patient's baseline is more informative than comparing to the population reference range. A rise >20% above baseline +2 ng/mL is suggestive of mast cell degranulation consistent with anaphylaxis.

Reference: Association of Anaesthetists – 2019 – Suspected anaphylaxis guidelines; RCUK – 2024 – Perioperative anaphylaxis