Tryptase (mast cell tryptase) serum
Measurement of serum mast cell tryptase level is used to confirm a mast cell degranulation event and is the only reliable laboratory marker of anaphylaxis. A mast cell tryptase level >20µg/L is one of the diagnostic criteria for mastocytosis.
The half-life of serum tryptase is 2-3 hours and so the timing of sample draw for tryptase testing is crucial, too early and there is a risk of falsely normal levels, too late and tryptase levels may have fallen back to within the normal range. UK NICE (CG134) recommend two tryptase samples be taken in the acute setting, immediately and within 1-2hours but no longer than 4 hours of the beginning of clinical symptoms, followed by a baseline tryptase sample taken over 24 hours after symptoms have resolved.
Anaphylaxis is not excluded if tryptase levels are within the normal range. A mast cell activation event can be demonstrated if acute tryptase level is equal to or greater than 1.2 x baseline tryptase + 2µg/l.
Causes of raised baseline serum tryptase levels include hereditary alpha tryptasemia (HAT), mastocytosis, helminth infection, metabolic syndromes and chronic renal failure.
Investigation of anaphylaxis and mastocytosis
<14.0 µg/l
Reference range currently under review
The Laboratory is currently unaccredited for tryptase tests due to a change in platform.
This test is not currently accredited
Record last updated
March 27, 2026
Sample Container
5ml SST Vacutainers (Rust top)
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Test Results
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Additional tests may be added by discussion with the relevant laboratory. The time limit for adding additional tests to a sample already received in the laboratory will depend on the type of sample and the department it was sent to.
Information on the repertoire of tests performed by pathology, including reference ranges, turnaround times and specimen requirements, can be found in the test directory.
Different tests have different sample stability requirements. If a comment on results indicates that the sample was delayed, the links below will indicate which tests may have been affected. This information is for serum or plasma samples.
For some tests, the impact of delay is consistent and these are marked with an arrow:
↑ indicates tests where delayed centrifugation results in falsely elevated results and the true level is likely lower than that reported.
↓ indicates tests where delayed centrifugation results in falsely lowered results and the true level is likely higher than that reported.
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Please interpret results with caution and consider the impact of any uncertainty.
The comment on the report will state how delayed the sample was. Please click the relevant link below to see which other tests may have been affected.
| >8h | >12h | >24h | >48h | >72h |
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NWLP operates UKAS accredited medical laboratories as per the references below. The current scope of accreditation for all NWLP’s laboratories can be found on the UKAS website.
UKAS accredited medical laboratory/medical diagnostic service:
- Clinical Biochemistry No. 8673
- Haematology and Blood Transfusion No. 8674
- Infection & Immunity Sciences (Including Immunology, Virology, Microbiology and Histocompatibility and Immunogenetics ) No. 8659
- Cellular Pathology (Including Histopathology, Cytology and Molecular Pathology) No. 9615
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UKAS requires the laboratories to be accredited for a particular repertoire/scope (ISO15189), any changes or additions to repertoire require assessment by UKAS (extension to scope).
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INSTRUCTION SHEET FOR BLOOD SAMPLE COLLECTION
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Our accreditations
Upholding excellence in diagnostic standards
Our laboratories are accredited by the UK Accreditation Service (UKAS) against the international standard ISO15189:2022. UKAS is the accreditation body for the UK that assesses medical laboratories.
Find out more about our accreditations on the UKAS website.
UKAS website