Tryptase Determination

Policy statement

Immune activation leading to anaphylactic reactions can be caused by a variety of IgE-mediated and non-IgE mediated mechanisms, including drugs, food ingestion and insect venoms. The intravenous route of drug administration is a potent source of immediate (IgE-mediated) hypersensitivity or direct histamine release (non-IgE-mediated) reactions. The severity of these reactions may range from minor histamine-mediated responses (flushing, mild urticaria) through to gross systemic disturbances including cardiovascular collapse, bronchospasm, cardiac arrest and death. Tryptase can be used to detect such reactions for diagnostic and medico-legal purposes and in order to define actions which will avoid future reactions.  Because of the potentially serious consequences of these assays, special care must be taken in recording results and information.

Correct interpretation of tryptase levels requires multiple samples and careful handling. It is important that clear records of sample time and date and clinical details are kept.

Samples required

  • Basic requirements: 2mL EDTA plasma or serum sample
  • Sample 1: As soon as possible after, or within one hour or, onset of reation.
  • Sample 2: 3-6 h post-reation (peak reaction time)
  • Sample 3: 24h post-reation (baseline)

Samples should taken as near to these times as possible. The requestor should note the time exactly. These time intervals are based on the half live of tryptase (2 hrs in vivo). Note that post-mortem tryptase is stable for longer.

Samples can be stored at 4oC for up to 3hrs in the ward/operating theatre during collection.

A single tryptase determination is of limited value and should be interpreted with caution.

Documentation Required

This should include the following if relevant (although any other factor which the anaesthetist/clinician thinks could be a cause of the reaction should be indicated, e.g. surgical stimulation, undiagnosed hypovolaemia etc):

  • Patient’s name, date of birth, hospital number, gender.
  • The sender and contact address
  • Surgical procedure.
  • Date and time of reaction.
  • Drugs administered (including premedication and sequences where possible).
  • Clinical manifestations.
  • Management of reaction and outcome (e.g. residual effects or death).
  • Previous medical and anaesthetic history if known.
  • Any particular risk factors? (e.g. known asthmatic, penicillin allergy, anaesthetic reaction etc).

Blood samples for plasma/serum tryptase assay should be separated as soon as possible, preferably within three hours of venesection. The plasma/serum should be stored at -20ºC until the full set has been collected.

Special Situations

It is recognised that on many occasions the above protocol will be unworkable and even that death may have intervened. Single blood samples, even -when collected post mortem, may still be of value in distinguishing unforeseen underlying causative pathology. In such cases telephone the laboratory to discuss the situation.


Plasma tryptase can be elevated in systemic mastocytosis. Here levels tend to be constantly raised. Mastocytosis involves the release of a-tryptase whereas anaphylaxis involves the release of b-tryptase. Both forms of tryptase are measured by this assay. However, Mastocytosis is a rare disorder.  Users should discuss cases with Consultants, Registrars or senior Scientist staff.

Page updated: 10/10/14 | Updated by: Anna McHugh