title: Increasing the accuracy of peanut allergy diagnosis by using Ara h 2.
abstract: BACKGROUND
  Measurement of whole peanut-specific IgE (sIgE) is often used to confirm sensitization but does not reliably predict allergy. Ara h 2 is the dominant peanut allergen detected in 90% to 100% of patients with peanut allergy and could help improve diagnosis.
  
  
  OBJECTIVE
  We sought to determine whether Ara h 2 testing might improve the accuracy of diagnosing peanut allergy and therefore circumvent the need for an oral food challenge (OFC).
  
  
  METHODS
  Infants from the population-based HealthNuts study underwent skin prick tests to determine peanut sensitization and subsequently underwent a peanut OFC to confirm allergy status. In a stratified random sample of 200 infants (100 with peanut allergy and 100 with peanut tolerance), whole peanut sIgE and Ara h 2 sIgE levels were quantified by using fluorescence enzyme immunoassay.
  
  
  RESULTS
  By using the previously published 95% positive predictive value of 15 kU(A)/L for whole peanut sIgE, a corresponding specificity of 98% (95% CI, 93% to 100%) was found in this study cohort. At the equivalent specificity of 98%, the sensitivity of Ara h 2 sIgE is 60% (95% CI, 50% to 70%), correctly identifying 60% of subjects with true peanut allergy compared with only 26% correctly identified by using whole peanut sIgE. We report that when using a combined approach of plasma sIgE testing for whole peanut followed by Ara h 2 for the diagnosis of peanut allergy, the number of OFCs required is reduced by almost two thirds.
  
  
  CONCLUSIONS
  Ara h 2 plasma sIgE test levels provide higher diagnostic accuracy than whole peanut plasma sIgE levels and could be considered a new diagnostic tool to distinguish peanut allergy from peanut tolerance, which might reduce the need for an OFC.
authors.affiliation: Murdoch Childrens Research Institute, Parkville, Australia.
authors.forename: Thanh D
authors.initials: TD
authors.lastname: Dang
authors.forename: Mimi
authors.initials: M
authors.lastname: Tang
authors.forename: Sharon
authors.initials: S
authors.lastname: Choo
authors.forename: Paul V
authors.initials: PV
authors.lastname: Licciardi
authors.forename: Jennifer J
authors.initials: JJ
authors.lastname: Koplin
authors.forename: Pamela E
authors.initials: PE
authors.lastname: Martin
authors.forename: Tina
authors.initials: T
authors.lastname: Tan
authors.forename: Lyle C
authors.initials: LC
authors.lastname: Gurrin
authors.forename: Anne-Louise
authors.initials: AL
authors.lastname: Ponsonby
authors.forename: Dean
authors.initials: D
authors.lastname: Tey
authors.forename: Marnie
authors.initials: M
authors.lastname: Robinson
authors.forename: Shyamali C
authors.initials: SC
authors.lastname: Dharmage
authors.forename: Katrina J
authors.initials: KJ
authors.lastname: Allen
mesh_terms: D055516:2S Albumins, Plant / Q000276:immunology; D000707:Anaphylaxis / Q000175:diagnosis / Q000276:immunology; D052179:Antigens, Plant / Q000276:immunology; D005260:Female; D006023:Glycoproteins / Q000276:immunology; D006801:Humans; D007073:Immunoglobulin E / Q000097:blood / Q000276:immunology; D007223:Infant; D008297:Male; D021183:Peanut Hypersensitivity / Q000175:diagnosis* / Q000276:immunology; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012882:Skin Tests / Q000379:methods
chemical_list: D055516:2S Albumins, Plant; D052179:Antigens, Plant; C078642:Ara h II protein, Arachis hypogaea; D006023:Glycoproteins; D007073:Immunoglobulin E