title: Tryptase levels in children presenting with anaphylaxis: Temporal trends and associated factors.
abstract: BACKGROUND
  The diagnosis of anaphylaxis currently relies on suggestive clinical history after exposure to a potential triggering factor because no reliable diagnostic marker is available to confirm the diagnosis.
  
  
  OBJECTIVE
  We aimed to evaluate tryptase levels in children with anaphylaxis and to examine predictors of elevated tryptase level (defined as ≥11.4 μg/L during reaction and for those with a baseline level, defined as a reaction level of at least 2 ng/mL + 1.2 × [postreaction tryptase level]).
  
  
  METHODS
  Children presenting with anaphylaxis to the Montreal Children's Hospital were recruited over a 4-year period. Symptoms, triggers, and management of anaphylaxis were documented. Levels during the reaction and approximately 9 months after the reaction were compared on the basis of paired means using the t distribution. Multivariate linear and logistic regressions were used to evaluate the association between tryptase levels and risk factors.
  
  
  RESULTS
  Over a 4-year period, 203 children had serum tryptase levels measured. Among these, 39 children (19.2%; 95% CI, 14.1%-25.4%) had elevated levels. Only severe reactions were associated with reaction levels of 11.4 μg/L or more (odds ratio, 6.5; 95% CI, 2.2-19.0). Milk-induced anaphylaxis and severe reactions were more likely associated with increased tryptase levels (beta-adjusted, 4.0; 95% CI, 0.95-7.0, and 7.5; 95% CI, 4.8-10.3, respectively). Reaction levels exceeding the threshold level of 2 ng/mL + 1.2 × (postreaction tryptase level) detected most of the anaphylactic reactions, particularly if baseline levels were taken within 2 months of the reaction.
  
  
  CONCLUSIONS
  Tryptase levels are particularly useful for the diagnosis of severe and/or milk-induced anaphylaxis. Assessing the difference between reaction and postreaction tryptase levels may improve diagnostic sensitivity.
authors.affiliation: Division of Allergy and Clinical Immunology, Department of Pediatrics, Montreal Children's Hospital, Montreal, Quebec, Canada.
authors.forename: Sarah
authors.initials: S
authors.lastname: De Schryver
authors.affiliation: Division of Paediatric Allergy and Clinical Immunology, Department of Paediatrics, University of Manitoba, Winnipeg, Manitoba, Canada.
authors.forename: Michelle
authors.initials: M
authors.lastname: Halbrich
authors.affiliation: Division of Rheumatology, Department of Medicine, University of Calgary, Calgary, Alberta, Canada.
authors.forename: Ann
authors.initials: A
authors.lastname: Clarke
authors.affiliation: Food Directorate, Health Canada, Ottawa, Ontario, Canada.
authors.forename: Sebastien
authors.initials: S
authors.lastname: La Vieille
authors.affiliation: Department of Emergency Medicine, Department of Pediatrics, Montreal Children's Hospital, Montreal, Quebec, Canada.
authors.forename: Harley
authors.initials: H
authors.lastname: Eisman
authors.affiliation: Division of Allergy and Clinical Immunology, Department of Pediatrics, Montreal Children's Hospital, Montreal, Quebec, Canada.
authors.forename: Reza
authors.initials: R
authors.lastname: Alizadehfar
authors.affiliation: Department of Epidemiology and Biostatistics, McGill University, Montreal, Quebec, Canada.
authors.forename: Lawrence
authors.initials: L
authors.lastname: Joseph
authors.affiliation: Department of Emergency Medicine, Hôpital du Sacré-Cœur, Montreal, Quebec, Canada.
authors.forename: Judy
authors.initials: J
authors.lastname: Morris
authors.affiliation: Division of Allergy and Clinical Immunology, Department of Pediatrics, Montreal Children's Hospital, Montreal, Quebec, Canada. Electronic address: moshebenshoshan@gmail.com.
authors.forename: Moshe
authors.initials: M
authors.lastname: Ben-Shoshan
mesh_terms: D000293:Adolescent; D000707:Anaphylaxis / Q000097:blood / Q000175:diagnosis* / Q000209:etiology; D015415:Biomarkers / Q000097:blood; D002648:Child; D002675:Child, Preschool; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007223:Infant; D016014:Linear Models; D016015:Logistic Models; D008297:Male; D011446:Prospective Studies; D012307:Risk Factors; D012720:Severity of Illness Index; D013997:Time Factors; D053802:Tryptases / Q000097:blood*
chemical_list: D015415:Biomarkers; D053802:Tryptases
keywords: Anaphylaxis; children; diagnosis; milk allergy; tryptase