title: Cat allergen-induced blood basophil reactivity in vitro predicts acute human nasal allergen challenge responses in vivo.
abstract: BACKGROUND
  Basophil histamine release (BHR) to allergen has been used as a confirmatory test to support the clinical diagnosis of allergic disease.
  
  
  OBJECTIVE
  Among subjects reporting respiratory cat allergy, we hypothesized that cat-induced BHR in vitro would predict nasal allergen challenge (NAC) response in that same individual. We therefore compared the magnitude of cat allergen-induced BHR to NAC outcome and serological measures of cat-specific IgE and the ratio of cat-specific IgE to total IgE.
  
  
  METHODS
  Forty-two subjects with a history of cat allergy, positive cat puncture skin test (PST) and detectable cat-specific IgE (> 0.1 kAU/L, ImmunoCap) participated with consent. Subjects were grouped as positive or negative cat allergen-induced BHR, with a positive result defined as the release of ≥ 20% of the total cellular histamine content. The majority of subjects also underwent a NAC with a positive result defined as ≥ 5 total sneezes.
  
  
  RESULTS
  Subjects with a positive compared with a negative cat allergen BHR had higher cat-specific IgE levels at 5.40 ± 1.24 kAU/L (n=25) vs. 1.55 ± 0.73 kAU/L (n=17, P=0.01) as well as a higher cat-specific IgE/total IgE ratio [6.1 ± 1.4% (n=25) vs. 1.6 ± 0.9% (n=17, P=0.01)]. Of the 31 subjects who underwent a NAC, a positive NAC was observed in 78% (18/23) with a positive cat allergen BHR compared with 37% (3/8) with a negative cat allergen BHR, giving a positive predictive value of 78% and a negative predictive value of 63%. The diagnostic sensitivity and specificity of a positive BHR to predict a positive NAC was 86% and 50%, respectively.
  
  
  CONCLUSIONS
  A positive cat allergen-induced BHR is associated with higher cat-specific IgE levels, a higher cat-specific to total IgE ratio and is predictive of a positive cat-induced NAC [ClinicalTrials.gov NCT00604786].
authors.affiliation: Johns Hopkins Asthma and Allergy Center, Baltimore, Maryland, USA.
authors.forename: M
authors.initials: M
authors.lastname: Paterniti
authors.forename: D C
authors.initials: DC
authors.lastname: Kelly
authors.forename: J A
authors.initials: JA
authors.lastname: Eckman
authors.forename: P M
authors.initials: PM
authors.lastname: Sterba
authors.forename: R G
authors.initials: RG
authors.lastname: Hamilton
authors.forename: B S
authors.initials: BS
authors.lastname: Bochner
authors.forename: D W
authors.initials: DW
authors.lastname: Macglashan
authors.forename: S S
authors.initials: SS
authors.lastname: Saini
mesh_terms: D000328:Adult; D000485:Allergens / Q000276:immunology*; D000818:Animals; D000918:Antibody Specificity / Q000276:immunology*; D001491:Basophils / Q000276:immunology*; D002415:Cats / Q000276:immunology*; D005260:Female; D006636:Histamine Release / Q000276:immunology*; D006801:Humans; D007073:Immunoglobulin E / Q000097:blood*; D008297:Male; D008875:Middle Aged; D009299:Nasal Provocation Tests; D011237:Predictive Value of Tests; D012130:Respiratory Hypersensitivity / Q000175:diagnosis* / Q000276:immunology; D012882:Skin Tests; D055815:Young Adult
chemical_list: D000485:Allergens; D007073:Immunoglobulin E