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Mastocytosis is a biological disorder that is characterized by an increased numbers of mast cells in the Gastrointestinal (GI) tract, skin, bone marrow, spleen, liver, and lymph node.

The World Health Organization (WHO) has a consensus on diagnostic criteria of mastocytosis.2

Diagnostic criteria in systemic mastocytosis2

A. Major criteria
1. Histological/immunohistochemical alterations: mast cell aggregates containing more than 15 mast cells in bone marrow sections
B. Minor criteria

1. Cytological alterations: >25% of morphologically abnormal mast cells

2. Detection of c-kit mutations on codon 816

3. Immunophenotypic alterations: expression of CD25 (± CD2) in mast cells from bone marrow, peripheral blood or other organs

4. Total serum tryptase levels persistently >20ng/mL (not applicable if there is a related blood disorder or evidence of acute mast cell release)

C. Diagnosis of systemic mastocytosis

a. at least 1 major criterion + 1 minor criterion

b. at least 3 minor criterion

The robustness of tryptase makes it a useful tool for confirming mast cell involvement.1

Together with clinical findings, tryptase test results can help you rule in systemic mastocytosis.

Making the Diagnosis: How Testing Can Help

Tryptase testing can measure the total level of tryptase released by mast cells into the circulation. This enables a healthcare provider to evaluate a person’s baseline tryptase level or any transient increases in the level of tryptase after a suspected allergic reaction. In healthy individuals, the tryptase baseline levels have been reported to range approximately between 1–15 μg/l.3,4

The prevalence of anaphylaxis in adults with the diagnosis of mastocytosis is reportedly as high as 49%, significantly higher than expected in the general population.1 In children, the risk to develop anaphylaxis is restricted to those with extensive skin symptoms and also a high baseline serum level of tryptase.1

ImmunoCAPTM Tryptase

ImmunoCAP Tryptase is an in vitro semi-quantitative assay for measurement of tryptase in human serum or plasma (EDTA, lithium heparin or sodium heparin). It is intended for in vitro diagnostic use as an aid in the clinical diagnosis of patients with a suspicion of systemic mastocytosis in conjunction with other clinical and laboratory findings.5

Allergy Testing

Conditions & Diseases

Understand allergic and autoimmune diseases.

  1. Brockow K, Metcalfe DD. Mastocytosis. Chem Immunol Allergy. 2010;95:110–24.  
  2. Valent P, Akin C, Metaclfe DD. Mastocytosis: 2016 updated WHO classification and novel emerging treatment concepts. Blood. 2017:129(11):1420-1427.
  3. Schwartz, LB. Diagnostic value of tryptase in anaphylaxis and mastocytosis. Immunol Allergy Clin N Am. 2006; 26:451-463.
  4. Komarow et al. Serum tryptase levels in atopic and nonatopic children. J Allergy Clin Immunol. 2009(124): 845-47.  
  5. PhadiaTM ImmunoCAPTM Tryptase Directions for Use for the Phadia 250 Laboratory System. Issued September 2017.