return to T index  

return to index page

Test Directory - Tryptase


Mast cell tryptase, MCT

Clinical Indications

Tryptase is a relatively mast-cell-specific protease that is released upon mast-cell degranulation; its plasma level peaks at 1 hour post event and may be detectable for up to 6 hours.

The finding an elevated serum tryptase level compared with a baseline level obtained when the patient is asymptomatic may confirm that symptoms were due to an anaphylactic /anaphylactoid reaction.

For use of plasma tryptase levels used in investigation of suspected adverse drug reaction there is a specific adverse drug reaction protocol.

Plasma tryptase levels are also useful in diagnosis and monitoring of urticaria pigmentosa (cutaneous mastocytosis) and systemic mastocytosis.
Recent evidence suggests that tryptase may also be useful in management of asthma patients with moderate to severe Type 1 (anaphylactic) allergy reactions.

Test Includes

Plasma tryptase

Request Form

Combined Pathology Blood form (Yellow/Black). 


Analysed by referral laboratory if specific criteria met.

Protein Ref. Unit, Northern General Sheffield Hospital.

Specific Criteria

Tryptase levels are indicated in anyone who presents with rapidly developing life-threatening problems involving: the airway (pharyngeal or laryngeal oedema) and/or breathing (bronchospasm with tachypnoe) and/or circulation (hypotension and/or tachycardia) and in most cases associated skin and mucosal changes should be classed as suspected anaphylactic reaction or suspected anaphylaxis.
Requests by Consultant Dermatologists for diagnosis or monitoring of urticaria pigmentosa on an annual basis. Specific requests from Dr Skibinska in asthma patients.

Sample Timing

For suspected anaphylactic reactions in adults take first sample for tryptase as soon as possible after emergency treatment has started and a second sample ideally within 1-2 hours (but not later than 4 hours) from the onset of the symptoms. In children consider taking 2 samples for tryptase (timing as above) for reactions thought to be venom-related, drug related or idiopathic. Patient should be informed that third sample for tryptase may be needed at specialist follow-up.

For investigation of adverse drug reactions please refer to adverse drug reaction protocol.

Turnaround Time

1 week




2 ml


Pink top (EDTA) blood tube.

Lab. Handling

Separate as soon as possible and store at -20C, send all samples and documentation by post.

Causes for Rejection 

Not meeting specific criteria for analysis. Unlabelled sample. No details regarding timing of onset of symptoms and/or blood collection time.

Reference Range

2.0 - 14.0 ug/L

Last edited 16/04/14