title: The 3rd International Standard for serum IgE: international collaborative study to evaluate a candidate preparation.
abstract: BACKGROUND
  The measurement of serum IgE aids in the diagnosis and management of atopic allergic disease and hyper-IgE immunodeficiency syndromes. The 2nd World Health Organization (WHO) International Reference Reagent (IRR) for serum IgE (75/502; 5000 IU/ampoule), is widely used to calibrate assays for serum IgE. Exhaustion of stocks of the 2nd IRR necessitated the production of a replacement preparation and its evaluation in an international collaborative study to determine its suitability to serve as the 3rd International Standard (IS) for serum IgE.
  
  
  METHODS
  Sera and defibrinated plasma with elevated IgE levels were pooled and lyophilised in ampoules. This preparation, coded 11/234, was assayed by 18 laboratories in 11 countries using commercial assay methodology for IgE, along with the 2nd IRR, 75/502, and two lyophilised serum samples.
  
  
  RESULTS
  Overall, there were no consistent differences in the way that the candidate IS (11/234), the IRR (75/502), and the two serum samples behaved in the assays with respect to linearity and parallelism. The mean IgE value of the candidate IS, 11/234, relative to the IRR, 75/502, was 13,411 IU/mL based on parallel line analysis of raw assay data at NIBSC, and 13,551 IU/mL based on the laboratories' own estimates after correcting for the values obtained for 75/502.
  
  
  CONCLUSIONS
  The use of 11/234 will ensure that assays for serum IgE continue to be well standardised. The preparation was established by the WHO Expert Committee on Biological Standardization as the 3rd IS for serum IgE with an assigned value of 13,500 IU/mL, corresponding to 6750 IU/ampoule.
authors.forename: Susan J
authors.initials: SJ
authors.lastname: Thorpe
authors.forename: Alan
authors.initials: A
authors.lastname: Heath
authors.forename: Bernard
authors.initials: B
authors.lastname: Fox
authors.forename: Dina
authors.initials: D
authors.lastname: Patel
authors.forename: William
authors.initials: W
authors.lastname: Egner
mesh_terms: D000704:Analysis of Variance; D001774:Blood Chemical Analysis / Q000592:standards* / Q000706:statistics & numerical data; D005612:Freeze Drying; D006801:Humans; D007118:Immunoassay / Q000592:standards* / Q000706:statistics & numerical data; D007073:Immunoglobulin E / Q000097:blood* / Q000302:isolation & purification; D007202:Indicators and Reagents / Q000592:standards; D007753:Laboratories; D059748:Proteolysis; D012015:Reference Standards; D014944:World Health Organization
chemical_list: D007202:Indicators and Reagents; D007073:Immunoglobulin E