title: Platelet-activating factor, histamine, and tryptase levels in human anaphylaxis.
abstract: BACKGROUND
  Platelet-activating factor (PAF) is an important mediator and correlates with anaphylaxis severity. How well PAF correlates with severity relative to histamine or tryptase is not known.
  
  
  OBJECTIVE
  To analyze the levels of PAF, histamine, and tryptase as a function of severity in patients with acute allergic reactions.
  
  
  METHODS
  PAF, histamine, and tryptase levels were measured in blood samples collected from 23 healthy volunteers and from 41 patients during acute allergic reactions. Reactions were stratified by severity from grade 1 (least severe) to grade 3 (most severe).
  
  
  RESULTS
  Among the 3 reaction grades, there were significant differences by ANOVA for PAF (P < .0001). The proportion of elevated PAF values increased across severity groups (P = .0009). Increased PAF levels were observed in 20%, 66.7%, and 100% of the patients with grades 1, 2, and 3 allergic reactions, respectively. While the proportion of elevated histamine values increased from 40% to 57% to 70% across grades 1, 2, and 3, respectively, these were not significantly different (P = .40). For tryptase, the proportion of elevated values increased monotonically from 0 in grade 1 to 4.8% in grade 2 to 60% in grade 3 (P = .0002).
  
  
  CONCLUSIONS
  The PAF level was significantly elevated in proportion to the severity of acute allergic reactions. Whereas the PAF level was elevated in all patients with severe anaphylaxis, this was not true for either histamine or tryptase. Neither histamine nor tryptase showed as good correlations with severity scores as did PAF. These data are consistent with a pivotal role for PAF as a mediator of anaphylaxis.
authors.affiliation: Division of Allergy and Clinical Immunology, Department of Medicine, St Michael's Hospital, University of Toronto, Toronto, Ontario, Canada. vadasp@smh.ca
authors.forename: Peter
authors.initials: P
authors.lastname: Vadas
authors.forename: Boris
authors.initials: B
authors.lastname: Perelman
authors.forename: Gary
authors.initials: G
authors.lastname: Liss
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000707:Anaphylaxis / Q000097:blood / Q000378:metabolism*; D003430:Cross-Sectional Studies; D005260:Female; D006632:Histamine / Q000097:blood*; D006801:Humans; D008297:Male; D008875:Middle Aged; D010972:Platelet Activating Factor / Q000378:metabolism*; D053802:Tryptases / Q000097:blood*; D055815:Young Adult
chemical_list: D010972:Platelet Activating Factor; D006632:Histamine; D053802:Tryptases