For optimum results a minimum of 2 samples should be taken, one within 30 minutes of the reaction and another six hours after. Ideally there would also be a sample taken at three hours.
This assay is available Monday to Friday and is not available on an urgent basis.
Post mortem samples should be taken within 48 hours of death.
CPR will raise serum/tissue tryptase levels.
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Uncertainty of measurement = 8%
| Age Range | Either Sex |
|---|---|
| All | < 11.4 |
TAT for tryptase is 1 to 2 working days.
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Elevated levels of tryptase are found in serum following anaphylaxis.
Ideally, take a sample immediately after the event, and another at about 6 hours after.
Human mast cells play a key role in inflammatory processes, particularly allergic reactions. They are found in increased numbers in some inflammatory conditions. Mast cells are mostly found in the dermis of the skin, throughout the lungs, and in mucosal and sub mucosal regions of the intestine. There are two types of mast cells defined by the proteases which they contain.
Mast cells bear high affinity receptors for the Fc portion of IgE. Linking of two or more receptor-bound IgE antibodies by allergen stimulates mast cells to release many of the mediators associated with allergic reactions such as histamine, prostaglandin D2, leukotriene C4, tryptase and chymase. Mast cells can also be activated by non-IgE mechanisms, including those involving complement types C3a and C5a.
Mast cell tryptase is a serine protease characterised as a tetramer with a molecular weight of 134kD. The enzyme is made up of four non-covalently bound subunits. Each subunit has one active enzymatic site. Two types of tryptase are expressed at the level of mRNA and protein a-tryptase and b-tryptase.
b-tryptase is selectively concentrated in the secretary granules of human mast cells, and the release of b-tryptase into the circulation serves as a clinical marker of mast cell activation.
Elevated levels of tryptase are found in serum following anaphylactic mast cell activation and in nasal fluid during allergic rhinitis. Elevated levels of serum tryptase are also found in systemic mastocytosis.
Tryptase levels measured in the perimortem period must be considered with caution as they may not always indicate anaphylaxis as the cause of death and levels may also vary according to sampling method and mode of death. Crush injuries are associated with non-specific increases in tryptase.
Clinical significance
Elevated levels of tryptase are found in serum following anaphylactic mast cell activation and in nasal fluid during allergic rhinitis. Elevated levels of serum tryptase are also found in systemic mastocytosis.
Even when in the normal range, after a possible anaphylaxis, changes in the level of serum tryptase between the acute result and the baseline level may still indicate mast cell degranulation and therefore anaphylaxis. The minimal elevation of the acute total serum tryptase level that is thought to be clinically significant has been suggested to be greater or equal to 2 + 1.2 times the baseline serum tryptase.
Tryptase levels measured in the perimortem period must be considered with caution as they may not always indicate anaphylaxis as the cause of death and levels may also vary according to sampling method and mode of death. Crush injuries are associated with non-specific increases in tryptase.
Reference:
Int Arch Allergy Immunol. 2012;157(3):215-25. doi: 10.1159/000328760. Epub 2011 Oct 27.
For further information contact the laboratory (09) 307 4949 ext 22000 or:
Associate Professor Rohan Ameratunga , Immunopathologist: Locator 93-5724
Or the LabPLUS Immunology Team
Separate sample within 4 hours and send supernatant at ambient temperature within 8 days.