title: An increase in serum tryptase even below 11.4 ng/mL may indicate a mast cell-mediated hypersensitivity reaction: a prospective study in Hymenoptera venom allergic patients.
abstract: BACKGROUND
  During a systemic hypersensitivity reaction (SR), an increase in serum tryptase compared to the baseline value is an indicator of mast cell activation, most often due to an IgE-mediated mechanism.
  
  
  OBJECTIVE
  To study the relevance of an increase in serum tryptase below the upper normal value of 11.4 ng/mL.
  
  
  METHODS
  Serum tryptase levels were measured in 35 patients with Hymenoptera venom hypersensitivity before and during venom exposure. Of these, 20 developed SR to stings or following venom injections during immunotherapy (reactors), while 15 tolerated reexposure to stings or venom injections during immunotherapy without SR (non-reactors). Serum tryptase was estimated at 2, 5 and 24 h after exposure and was compared to a baseline value obtained before or at least 72 h after exposure.
  
  
  RESULTS
  Considering circadian variation of serum tryptase, a relative increase to ≥135% of the baseline value (relative delta bound) was defined to indicate mast cell activation. Such an increase was observed in 17 of 20 reactors (85%), but none of 15 non-reactors. A serum tryptase of ≥11.4 ng/mL following venom exposure was observed in eight of the 20 reactors (40%) and 2 (13.3%) of the 15 non-reactors. Both these non-reactors also had an elevated baseline serum tryptase.
  
  
  CONCLUSIONS
  Serum tryptase values obtained during a suspected hypersensitivity reaction must always be compared to a baseline value. A relative tryptase increase to ≥135% of the baseline value during a suspected hypersensitivity reaction indicates mast cell activation even below 11.4 ng/mL.
authors.affiliation: Allergiestation, Medizinische Klinik, Spital Netz Bern Ziegler, Bern, Switzerland.
authors.forename: M
authors.initials: M
authors.lastname: Borer-Reinhold
authors.forename: G
authors.initials: G
authors.lastname: Haeberli
authors.forename: M
authors.initials: M
authors.lastname: Bitzenhofer
authors.forename: P
authors.initials: P
authors.lastname: Jandus
authors.forename: O
authors.initials: O
authors.lastname: Hausmann
authors.forename: M
authors.initials: M
authors.lastname: Fricker
authors.forename: A
authors.initials: A
authors.lastname: Helbling
authors.forename: U
authors.initials: U
authors.lastname: Müller
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000707:Anaphylaxis / Q000097:blood / Q000276:immunology; D000818:Animals; D001180:Arthropod Venoms / Q000276:immunology*; D005260:Female; D006801:Humans; D006927:Hymenoptera / Q000276:immunology*; D006969:Hypersensitivity, Immediate / Q000097:blood* / Q000276:immunology*; D007073:Immunoglobulin E / Q000097:blood / Q000276:immunology; D007299:Insect Bites and Stings / Q000276:immunology; D008297:Male; D008407:Mast Cells / Q000276:immunology*; D008875:Middle Aged; D012016:Reference Values; D053802:Tryptases / Q000097:blood*; D055815:Young Adult
chemical_list: D001180:Arthropod Venoms; D007073:Immunoglobulin E; D053802:Tryptases