Tryptase (Mast Cell Tryptase)

This test measures total tryptase (alpha and beta tryptase). Tryptase is the most abundant protein component of human mast cell secretory granules.^1,2 Serum levels generally reflect the extent of mast cell activation either by IgE- or non-IgE-mediated mechanisms. Basophils also produce small amounts of tryptase.

Tryptase is often ordered as part of the diagnostic assessment of a patient suspected of having mastocytosis (either cutaneous or systemic).^3-5 Serum levels are thought to correlate with mast cell "burden" in these patients.⁵ Mastocytosis is considered in the differential diagnosis of patients that experience severe allergic reactions without any identifiable specific trigger. Systemic mastocytosis can produce symptoms suggestive of organ involvement, such as peptic ulcers, chronic diarrhea, and joint pain. These patients may display evidence of enlargement of the liver, spleen, or lymph nodes. There may be skin involvement with rashes or characteristic red blistering lesions.

Tryptase may be ordered to help confirm anaphylaxis as the cause of an individual's acute symptoms, especially when the diagnosis is not clear and/or the symptoms are recurrent.^6,7 With anaphylaxis, tryptase levels typically peak about one to two hours after symptoms begin and then decline slowly within the next three to six hours. The biological half-life for tryptase is about two hours.

Systemic mastocytosis is a risk factor for anaphylactic reactions, particularly in response to drugs^8,9 and insect stings.^10-15 Patients with elevated baseline tryptase levels may be at increased risk for severe anaphylactic reactions. The risk associated with baseline elevated tryptase levels is greater in individuals with a known history of severe systemic reactions. Transiently increased tryptase levels measured during severe reaction to an allergen, such as insect venom or an anesthetic drug, suggest that mast cell activation may have had a role in causing the reaction.

Pathological increased levels of tryptase reflect the mast cell burden in certain hematological abnormalities and neoplasms, irrespective if systemic mastocytosis is established or not.¹⁶ Hematological disorders that involve uncontrolled growth of immature myeloid cells in the bone marrow and/or the circulation can produce increased serum tryptase levels. Several therapeutic drugs have been developed for cytoreductive therapy of systemic mastocytosis and hematological neoplasms.¹⁷ During treatment tryptase measurements is a useful monitoring and prognostic tool.

1. Schwartz LB. Diagnostic value of tryptase in anaphylaxis and mastocytosis. Immunol Allergy Clin N Am. 2006; 26(3):451-463. PubMed 16931288

2. Metcalfe DD, Boyce JA. Mast cell biology in evolution. J Allergy Clin Immunol. 2006; 117(6):1227-1229. PubMed 16750978

3. Sperr WR, Jordan J-H, Fiegl M, et al. Serum tryptase levels in patients with mastocytosis: Correlation with mast cell burden and implication for defining the category of disease. Int Arch Allergy Immunol. 2002; 128(2):136-141. PubMed 12065914

4. Donker ML, van Doormaal JJ, van Doormaal FF, et al. Biochemical markers predictive for bone marrow involvement in systemic mastocytosis. Haematologica. 2008; 93(1):120-123. PubMed 18166795

5. Valent P. Diagnostic evaluation and classification of mastocytosis. Immunol Allergy Clin N Am. 2006; 26(3):515-534. PubMed 16931291

6. Schwartz LB, Yunginger JW, Miller J, et al. Time course of appearance and disappearance of human mast cell tryptase in the circulation after anaphylaxis. J Clin Invest. 1989; 83(5):1551-1555. PubMed 2468689

7. Joint Task Force on Practice Parameters; American Academy of Allergy, Asthma and Immunology; American College of Allergy, Asthma, and Immunology; Joint Council of Allergy, Asthma, and Immunology. The diagnosis and management of anaphylaxis: An updated practice parameter. J Allergy Clin Immunol. 2005; 115(3 Suppl 2):S483-523. PubMed 15753926

8. Dybendal T, Guttormsen AB, Elsayed S, et al. Screening for mast cell tryptase and serum IgE antibodies in 18 patients with anaphylactic shock during general anesthesia. Acta Anaesthesiol Scand. 2003; 47(10):1211-1218. PubMed 14616317

9. Ebo DG, Fisher MM, Hagendorens MM, et al. Anaphylaxis during anesthesia: Diagnostic approach. Allergy. 2007, 62(5):471-487. PubMed 17441788

10. Bonadonna P, Zanotti R, Müller U. Mastocytosis and insect venom allergy. Curr Opin Allergy Clin Immunol. 2010; 10(4):347-353. PubMed 20485157

11. Bonadonna P, Perbellini O, Passalacqua G, et al. Clonal mast cell disorders in patients with systemic reactions to hymenoptera stings and increased serum tryptase levels. J Allergy Clin Immunol. 2009; 123(3):680-686. PubMed 19135713

12. Haeberli G, Brönnimann M, Hunziker T, et al. Elevated basal serum tryptase and hymenoptera venom allergy: Relation to severity of sting reactions and to safety and efficacy of venom immunotherapy. Clin Exp Allergy. 2003; 33(9):1216-1220. PubMed 12956741

13. Biló BM, Rueff F, Mosbech H, et al. Diagnosis of hymenoptera venom allergy. Allergy. 2005; 60(11):1339-1349. PubMed 16197464

14. Bonifazi F, Jutel M, Biló BM, et al; EAACI Interest Group on Insect Venom Hypersensitivity. Prevention and treatment of hymenoptera venom allergy: Guidelines for clinical practice. Allergy. 2005; 60(12):1459-1470. PubMed 16266376

15. Kucharewicz I, Bodzenta-Lukaszyk A, Szymanski W, et al. Basal serum tryptase level correlates with severity of hymenoptera sting and age. J Investig Clin Immunol. 2007; 17(2):65-69. PubMed 17460943

16. Sperr WR, Mitterbauer M, Mitterbauer G, et al. Quantitation of minimal residual disease in acute myeloid leukemia by tryptase monitoring identifies a group of patients with a high risk of relapse. Clin Cancer Res. 2005; 11(18):6536-6543. PubMed 16166430

17. Butterfield JH, Tefferi A, Kozuh GF, et al. Successful treatment of systemic mastocytosis with high-dose interferon-alfa: Long-term follow-up of a case. Leukemia Research. 2005; 29(2):131-134. PubMed 15607359

ImmunoCAP® Tryptase Conjugate 50 [package insert]. Portage, Mich: USA Phadia US Inc;December 9, 2010.