Mast Cell Tryptase

Mast cell tryptase is released during the anaphylactic reaction and may be measured in the blood.

It reaches its peak blood concentration approximately 1-2 hours after the reaction. This is useful to aid later diagnosis and treatment and can help in the diagnosis in uncertain cases.

The half-life of tryptase is short (approximately 2 hours) and concentrations may be back to normal within 6-8 hours, so timing of any blood samples is very important.

The Resuscitation Council recommend that three tryptase levels are taken:

• As soon as resuscitation has started
• 1-2 hours after symptoms have started
• 24 hours later or in convalescence (some people have raised baseline tryptase levels)

Current NICE guidelines recommend all adults and young people over 16yrs who present with a suspected anaphylactic reaction should have a sample taken as soon as possible after emergency treatment has started, and a second sample ideally within 1-2 hours (but no later than 4 hours) from the onset of symptoms.

Testing should be considered in all children under 16yrs who present with suspected venom-related, drug-related or idiopathic anaphylaxis only.