title: The utility of serum tryptase in the diagnosis of food-induced anaphylaxis.
abstract: OBJECTIVE
  This study investigates the utility of serum tryptase for the confirmation of shrimp-induced anaphylaxis.
  
  
  METHODS
  Patients with a history of shrimp allergy and positive skin prick tests (SPT) to commercial shrimp extract were recruited for shrimp challenges. Serum total tryptase was obtained at baseline and 60 min (peak) after the onset of symptoms.
  
  
  RESULTS
  Thirty-nine patients were challenged. There were 12 patients with anaphylaxis, 20 with mild reactions and 7 without symptoms (control group). Characteristic features and baseline tryptase were not different among the 3 groups. The peak tryptase levels were higher than the baseline in anaphylaxis and mild reaction groups (P<0.05). The delta-tryptase (peak minus baseline) and the tryptase ratio (peak divided by baseline) in the anaphylaxis group were higher than the mild reaction and control groups (P<0.01). The optimum cut-off for peak tryptase to confirm anaphylaxis was 2.99 µg/L with 50% sensitivity, 85% specificity, 3.33 positive likelihood ratio (LR) and 0.59 negative LR. The manufacturer's cut-off for peak tryptase was >11.4 µg/L with 17% sensitivity, 100% specificity, infinity positive LR and 0.83 negative LR. The best cut-off for delta-tryptase was ≥0.8 µg/L with 83% sensitivity, 93% specificity, 11.86 positive LR and 0.18 negative LR. The best cut-off for tryptase ratio was ≥1.5 with 92% sensitivity, 96% specificity, 23 positive LR and 0.08 negative LR.
  
  
  CONCLUSIONS
  The peak tryptase level should be compared with the baseline value to confirm anaphylaxis. The tryptase ratio provide the best sensitivity, specificity, positive and negative LR than a single peak serum tryptase for the confirmation of shrimp-induced anaphylaxis.
authors.affiliation: Department of Pediatrics, School of Medicine, Institute of Medicine, Suranaree University of Technology, Nakhonratchasima, Thailand.
authors.forename: Patcharaporn
authors.initials: P
authors.lastname: Wongkaewpothong
authors.affiliation: Division of Allergy and Immunology, Department of Pediatrics, Faculty of Medicine Siriraj Hospital Mahidol University, Bangkok, Thailand.
authors.forename: Punchama
authors.initials: P
authors.lastname: Pacharn
authors.affiliation: Division of Allergy and Immunology, Department of Pediatrics, Faculty of Medicine Siriraj Hospital Mahidol University, Bangkok, Thailand.
authors.forename: Chaweewan
authors.initials: C
authors.lastname: Sripramong
authors.affiliation: Division of Allergy and Immunology, Department of Pediatrics, Faculty of Medicine Siriraj Hospital Mahidol University, Bangkok, Thailand.
authors.forename: Siribangon
authors.initials: S
authors.lastname: Boonchoo
authors.affiliation: Institute of Molecular Biosciences, Mahidol University, Nakhonpathom, Thailand.
authors.forename: Surapon
authors.initials: S
authors.lastname: Piboonpocanun
authors.affiliation: Division of Allergy and Immunology, Department of Pediatrics, Faculty of Medicine Siriraj Hospital Mahidol University, Bangkok, Thailand.
authors.forename: Nualanong
authors.initials: N
authors.lastname: Visitsunthorn
authors.affiliation: Division of Allergy and Immunology, Department of Pediatrics, Faculty of Medicine Siriraj Hospital Mahidol University, Bangkok, Thailand.
authors.forename: Pakit
authors.initials: P
authors.lastname: Vichyanond
authors.affiliation: Division of Allergy and Immunology, Department of Pediatrics, Faculty of Medicine Siriraj Hospital Mahidol University, Bangkok, Thailand.
authors.forename: Orathai
authors.initials: O
authors.lastname: Jirapongsananuruk
keywords: Anaphylaxis; food; shrimp; tryptase