title: Measurement of inaccuracy and imprecision of HCG methods using dilutions of the WHO 4th IS-HCG standard and a pregnant patient's serum.
abstract: BACKGROUND
  Differences in human chorionic gonadotropin (hCG) results obtained by seven different methods were documented by analyzing dilutions of the WHO 4th International Standard (IS) and a pregnant patient's serum.
  
  
  METHODS
  Biases of +30.9 to -37.5% and +36.8 to -36.1% from the target concentration were found for the WHO 4th IS and patient sample dilutions, respectively.
  
  
  RESULTS
  Imprecision was calculated from replicate measurements of hCG on the different sample dilutions. Imprecision ranged from 1.0% to 18.9% and 1.1% to 5.3% for the WHO 4th IS and patient sample dilutions, respectively. Using a maximum allowable error of 12.5% for hCG measurements, we found that two instruments were so biased that their hCG measurements could not be interchanged with hCG values produced by any of the other systems.
  
  
  CONCLUSIONS
  It is ideal to use only one hCG methodology for the serial monitoring of hCG; otherwise, hCG methods should be carefully chosen to minimize inter-method bias.
authors.affiliation: Department of Laboratory Medicine and Pathology, University of Alberta Hospital, Alberta, Edmonton, Canada T6G 2B7. trefor.higgins@dkml.com
authors.forename: Trefor N
authors.initials: TN
authors.lastname: Higgins
authors.forename: Atef N
authors.initials: AN
authors.lastname: Hanna
authors.forename: Tammy L
authors.initials: TL
authors.lastname: Hofer
authors.forename: George S
authors.initials: GS
authors.lastname: Cembrowski
mesh_terms: D015982:Bias; D015415:Biomarkers; D006063:Chorionic Gonadotropin / Q000097:blood* / Q000592:standards*; D005260:Female; D006801:Humans; D007124:Immunoenzyme Techniques / Q000295:instrumentation; D008297:Male; D011247:Pregnancy; D011786:Quality Control; D011933:Reagent Kits, Diagnostic / Q000592:standards; D012015:Reference Standards; D012016:Reference Values; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
chemical_list: D015415:Biomarkers; D006063:Chorionic Gonadotropin; D011933:Reagent Kits, Diagnostic