title: Significant, quantifiable differences exist between IgG subclass standards WHO67/97 and ERM-DA470k and can result in different interpretation of results.
abstract: OBJECTIVE
  Accurate measurement of IgG subclass (IgGSc) levels are essential to aid in the diagnosis of disease states such as primary immunodeficiencies. However, there is no single standardisation of nephelometric and turbidimetric assays for these analytes and two reference materials have been utilised. We expand on previous reports and present data from a multi-site analysis that both identifies and quantitatively defines the differences in calibration resulting from the use of different reference materials.
  
  
  METHODS
  IgGSc antibodies in the serum specimens and reference materials were measured according to the manufacturers' instructions using commercially available IgGSc assays or components.
  
  
  RESULTS
  Data from four independent sites showed that in spite of the different commercial suppliers of IgGSc assays calibrating to different reference materials, ERM-DA470k and WHO67 /97, the resulting calibrations were comparable for IgG1 and IgG2. However, for IgG3 and IgG4 the calibrations were significantly different. The use of assay specific normal ranges should compensate for these calibration differences, however, the two manufacturers' assays can give differing clinical classifications. The agreement between the different manufacturers' IgGSc assays was between 85.1% and 95.8% for all IgGSc assays, the discordance of sample classification for IgG1 and IgG2 assays was approximately 12% and 15% respectively, whilst that for IgG3 and IgG4 was 4% and 13% respectively.
  
  
  CONCLUSIONS
  We discuss the similarities and differences between assays that utilise the different reference materials.
authors.affiliation: Binding Site Group Limited, 8 Calthorpe Road, Birmingham B15 1QT, United Kingdom.
authors.forename: Calum
authors.initials: C
authors.lastname: Wilson
authors.forename: Rosemary
authors.initials: R
authors.lastname: Ebling
authors.forename: Clara
authors.initials: C
authors.lastname: Henig
authors.forename: Tanya
authors.initials: T
authors.lastname: Adler
authors.forename: Roza
authors.initials: R
authors.lastname: Nicolaevski
authors.forename: Mira
authors.initials: M
authors.lastname: Barak
authors.forename: John
authors.initials: J
authors.lastname: Cazabon
authors.forename: Diane
authors.initials: D
authors.lastname: Maisin
authors.forename: Thibault
authors.initials: T
authors.lastname: Lepoutre
authors.forename: Damien
authors.initials: D
authors.lastname: Gruson
authors.forename: Richard G
authors.initials: RG
authors.lastname: Hughes
authors.forename: Antony R
authors.initials: AR
authors.lastname: Parker
mesh_terms: D000328:Adult; D002138:Calibration; D003627:Data Interpretation, Statistical; D006801:Humans; D007118:Immunoassay; D007074:Immunoglobulin G / Q000097:blood* / Q000145:classification*; D012016:Reference Values; D014944:World Health Organization
chemical_list: D007074:Immunoglobulin G
keywords: IgG sublcass; Immunology; Result interpretation