title: Ara h 2 and Ara 6 are the best predictors of severe peanut allergy: a double-blind placebo-controlled study.
abstract: BACKGROUND
  Component-resolved diagnostics offers a modern tool in peanut allergy, but studies applying consistently double-blind placebo-controlled challenges are lacking. We aimed to optimize diagnostics for moderate-to-severe peanut allergy in a birch-endemic region and to create an oral-peanut challenge with its allergen activity characterized.
  
  
  METHODS
  We performed double-blind placebo-controlled peanut challenges for a referred sample of 6- to 18-year-olds with peanut sensitization or a high suspicion of peanut allergy, including anaphylaxis. We measured specific IgE (sIgE) to Ara h 1, 2, 3, 6, 8, and 9. Testing of allergen activity of the challenge products was by IgE microarray inhibition.
  
  
  RESULTS
  Of the 102 patients, 69 were challenge positive: 25 (36%) had severe, 36 (52%) moderate, and 8 (12%) mild symptoms; 38 (37%) received adrenalin. SIgE to Ara h 6 AUC 0.98 (95%CI, 0.96-1.00) was the best marker of moderate-to-severe allergy. When sIgE to Ara h 2 and Ara h 6 was measured together, all (100%) severe reactions at low doses were successfully diagnosable. SIgE to Ara h 8 had no diagnostic value, AUC 0.42 (95%CI, 0.30-0.52). Both nonroasted and roasted peanut inhibited 100% of IgE binding to Ara h 1, 2, 3, and 6. Nonroasted peanut inhibited 87% of IgE binding to Ara h 8, roasted inhibited 30%. The products lacked Ara h 9 activity.
  
  
  CONCLUSIONS
  Co-sensitization to Ara h 2 and Ara h 6 was associated with severe reactions distinguishing severe allergy from mild symptoms. SIgE to Ara h 8 added no diagnostic value. Component-resolved diagnostics reduce the need for oral challenges in peanut allergy.
authors.affiliation: The Skin and Allergy Hospital, University of Helsinki and Helsinki University Hospital, Helsinki, Finland.
authors.forename: A K
authors.initials: AK
authors.lastname: Kukkonen
authors.affiliation: The Skin and Allergy Hospital, University of Helsinki and Helsinki University Hospital, Helsinki, Finland.
authors.forename: A S
authors.initials: AS
authors.lastname: Pelkonen
authors.affiliation: The Skin and Allergy Hospital, University of Helsinki and Helsinki University Hospital, Helsinki, Finland.
authors.forename: S
authors.initials: S
authors.lastname: Mäkinen-Kiljunen
authors.affiliation: The Skin and Allergy Hospital, University of Helsinki and Helsinki University Hospital, Helsinki, Finland.
authors.forename: H
authors.initials: H
authors.lastname: Voutilainen
authors.affiliation: The Skin and Allergy Hospital, University of Helsinki and Helsinki University Hospital, Helsinki, Finland.
authors.forename: M J
authors.initials: MJ
authors.lastname: Mäkelä
mesh_terms: D055516:2S Albumins, Plant / Q000276:immunology*; D000293:Adolescent; D000485:Allergens / Q000276:immunology; D000918:Antibody Specificity / Q000276:immunology; D052179:Antigens, Plant / Q000276:immunology*; D010367:Arachis / Q000009:adverse effects*; D002648:Child; D005260:Female; D006023:Glycoproteins / Q000276:immunology*; D006801:Humans; D007114:Immunization; D007073:Immunoglobulin E / Q000276:immunology; D008297:Male; D021183:Peanut Hypersensitivity / Q000175:diagnosis* / Q000276:immunology*; D012372:ROC Curve; D012307:Risk Factors; D012720:Severity of Illness Index; D012882:Skin Tests
chemical_list: D055516:2S Albumins, Plant; D000485:Allergens; D052179:Antigens, Plant; C492737:Ara h 6 allergen, Arachis hypogaea; C078642:Ara h II protein, Arachis hypogaea; D006023:Glycoproteins; D007073:Immunoglobulin E
keywords: Ara h 2; Ara h 6; Ara h 8; double-blind placebo-controlled food challenge; peanut allergy