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Item Value
Approval req'd? No
Available Stat? No
Test code BTRP
Performed by Medical College of Virginia via Quest
Sendout? Yes
Method Enzyme linked immunosorbent immunoassay
Container type Red top
Amount to Collect 2 mL blood
Sample type Serum
Preferred volume 1 mL serum
Min. Volume 0.6 mL serum
Processing notes Separate serum from cells as soon as possible. Freeze at -20C and ship frozen. Order Quest # 10497N.
Units ng/mL
Normal range See Additional Information
Synonyms Total tryptase
Turn around times Test performed at Medical College of Virginia, Richmond, VA 23219 via Quest Nichols lab. Test is batched.
Additional information B-tryptase levels in blood are a measure of mast cell activation. The assay uses a capture mAb that preferentially recognizes B-tryptase. Normal serum levels are < 1 ng/mL. Levels > 1 ng/mL indicate mast cell activation. After insect sting-mediated systemic anaphylaxis, B-tryptase levels peak 30-60 minutes after the sting and then decline with a 1 1/2 of 2 hours. Peak levels are typically > 5 ng/mL in mast cell-dependent systemic anaphylaxis of sufficient severity to cause hypotension. Levels determined more than 3 to 4 hours after the clinical onset of anaphylaxis will be correspondingly lower and could fall within the normal or mildly elevated range in spite of mast cell activation having occurred. In postmortem sera, a peak B-tryptase level > 10 ng/mL is needed before systemic anaphylaxis should be considered in the cause of death. An apparent elevated level of B-tryptase in a baseline sample suggests systemic mastocytosis (see below).

a-protyptase levels in blood are a measure of mast cell number, and can be estimated by subtracting B-tryptase from total tryptase. The total tryptase (UniCAP) assay uses a capture mAb that recognizes both a-protryptase and B-tryptase. Normal serum levels of total tryptase average 5 ng/mL and range from 1 to 10 ng/mL. Baseline levels > 20 ng/mL, particularly when the ratio of a-protryptase to B-tryptase is > 10 suggest systemic mastocytosis be considered. Because the mAb used to detect B-tryptase in the B-tryptase assay weakly cross-reacts with a-protryptase, high levels of a-protryptase can result in low apparent levels of B-tryptase.

1. Schwartz, L.B., et al: Tryptase levels as an indicator of mast cell activation in systemic anaphylaxis and mastocytosis. New Engl J. Med., 316:1622-1626, 1987. B-tryptase
2. Schwartz, L.B., et al: The time course of appearance and disappearance of human mast cell tryptase in the circulation after anaphylaxis. J. Clin. Invest. 83:1551-1555, 1989. B-tryptase
3. Yunginger, J.W., et al: Laboratory investigation of deaths due to anaphylaxis. J. Forensic Sci., 36:857-865, 1991. B-tryptase
4. Enander, I., et al: A new radioimmunoassay for human mast cell tryptase using monoclonal antibodies. J. Immunol. Meth. 138:39-46, 1991. B-tryptase
5. Van Der Linden, P.G., et al: Insect-sting challenge in 138 patients: Relation between clinical severity of anaphylaxis and mast cell activation. J. Allergy Clin. Immunol. 90:110, 1992. B-tryptase
6. Schwartz, L.B.; Laboratory assessment of immediate hypersensitivity and anaphylaxis; utilization of tryptase as a marker of mast cell-dependent events, in Huston DP(ed): Immunology and Allergy Clinics of North America: Diagnostic Laboratory Immunology, Philadelphia, W.B. Saunders
Co., 1994 pp. 339-350. B-tryptase.
7. Schwartz, L.B., et al: Development of a new, more sensitive immunoassay for human tryptase: use in systemic anaphylaxis. J. Clin. Immunol. 14:190-204, 1994. a-trypase + B-tryptase
8. Schwartz, L.B., et al; The alpha form of tryptase is the predominant type present in blood at baseline in normal subjects, and is elevated in those with systemic mastocytosis. J. Clin. Invest. 96:2702-2710, 1995. a-tryptase and B-tryptase
CPT coding 83520-90
LOINC code 21582-2
Last Updated 12/17/2012 4:46:56 PM
Entry Number 83
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