title: Extension of food allergen specific IgE ranges from the ImmunoCAP to the IMMULITE systems.
abstract: BACKGROUND
  Quantitative measures of food specific IgE antibody using the Phadia ImmunoCAP method have documented value in the diagnosis of food allergy.
  
  
  OBJECTIVE
  To define factors that could be used to relate IMMULITE-measured IgE antibody levels for chicken egg white, cow's milk, and peanut into ImmunoCAP-comparable quantities that could then be correlated with published levels that have been generated with the ImmunoCAP system.
  
  
  METHODS
  Serum samples from 328 patients (median age, 5.4 years; age range, 1-18 years; 32% female) who were known to be IgE positive (>0.1 kU/L) to chicken egg white (n = 120), cow's milk (n = 135), and/or peanut (n = 304) were analyzed in both the ImmunoCAP and IMMULITE autoanalyzers.
  
  
  RESULTS
  IgE antibody levels from both assays for each of the 3 food specificities were highly correlated: r(2)= 0.95 for egg white, r(2) = 0.93 for milk, and r(2) = 0.95 for peanut (P < .001). Empirically determined IMMULITE/ImmunoCAP ratios (mean ± 1 SD) were 4.85 ± 1.79 kU/L (egg), 2.33 ± 1.0 kU/L (milk), and 1.86 ± 0.98 kU/L (peanut). For milk and peanut, the IgE antibody levels for individuals who either passed or failed a food challenge were not significantly different between the assay methods. Because of the small sample size of egg white challenged patients, no statistical analysis was performed.
  
  
  CONCLUSIONS
  These data indicate that specific IgE levels to egg white, milk, and peanut measured by the IMMULITE and ImmunoCAP systems are highly correlated and that differences between the systems are circumscribed and modest (IMMULITE was a mean of 2- to 5-fold higher than ImmunoCAP).
authors.affiliation: Allergy and Clinical Immunology, Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland 21224, USA. rhamilt@jhmi.edu
authors.forename: Robert G
authors.initials: RG
authors.lastname: Hamilton
authors.forename: Kim
authors.initials: K
authors.lastname: Mudd
authors.forename: Mirinda Anderson
authors.initials: MA
authors.lastname: White
authors.forename: Robert A
authors.initials: RA
authors.lastname: Wood
mesh_terms: D000293:Adolescent; D000485:Allergens / Q000276:immunology; D000818:Animals; D002417:Cattle; D002645:Chickens; D002648:Child; D002675:Child, Preschool; D004527:Egg Proteins / Q000276:immunology; D005260:Female; D005512:Food Hypersensitivity / Q000175:diagnosis* / Q000453:epidemiology* / Q000276:immunology; D006801:Humans; D007073:Immunoglobulin E / Q000097:blood; D007223:Infant; D008297:Male; D008894:Milk Proteins / Q000276:immunology; D012016:Reference Values; D012698:Serologic Tests / Q000592:standards* / Q000706:statistics & numerical data
chemical_list: D000485:Allergens; D004527:Egg Proteins; D008894:Milk Proteins; D007073:Immunoglobulin E