title: Report of the IFCC Working Group for Standardization of Thyroid Function Tests; part 1: thyroid-stimulating hormone.
abstract: BACKGROUND
  Laboratory testing of serum thyroid-stimulating hormone (TSH) is an essential tool for the diagnosis and management of various thyroid disorders whose collective prevalence lies between 4% and 8%. However, between-assay discrepancies in TSH results limit the application of clinical practice guidelines.
  
  
  METHODS
  We performed a method comparison study with 40 sera to assess the result comparability and performance attributes of 16 immunoassays.
  
  
  RESULTS
  Thirteen of 16 assays gave mean results within 10% of the overall mean. The difference between the most extreme means was 39%. Assay-specific biases could be eliminated by recalibration to the overall mean. After recalibration of singlicate results, all assays showed results within the biological total error goal (22.8%), except for 1 result in each of 4 assays. For a sample with a TSH concentration of 0.016 mIU/L, 6 assays either did not report results or demonstrated CVs >20%. Within-run and total imprecision ranged from 1.5% to 5.5% and 2.5% to 7.7%, respectively. Most assays were able to match the internal QC targets within 5%. Within-run drifts and shifts were observed.
  
  
  CONCLUSIONS
  Harmonization of TSH measurements would be particularly beneficial for 3 of the 16 examined assays. These data demonstrate that harmonization may be accomplished by establishing calibration traceability to the overall mean values for a panel of patient samples. However, the full impact of the approach must be further explored with a wider range of samples. Although a majority of assays showed excellent quality of performance, some would benefit from improved within-run stability.
authors.affiliation: Laboratory for Analytical Chemistry, Faculty of Pharmaceutical Sciences, Ghent University, Ghent, Belgium. Linda.thienpont@ugent.be
authors.forename: Linda M
authors.initials: LM
authors.lastname: Thienpont
authors.forename: Katleen
authors.initials: K
authors.lastname: Van Uytfanghe
authors.forename: Graham
authors.initials: G
authors.lastname: Beastall
authors.forename: James D
authors.initials: JD
authors.lastname: Faix
authors.forename: Tamio
authors.initials: T
authors.lastname: Ieiri
authors.forename: W Greg
authors.initials: WG
authors.lastname: Miller
authors.forename: Jerald C
authors.initials: JC
authors.lastname: Nelson
authors.forename: Catherine
authors.initials: C
authors.lastname: Ronin
authors.forename: H Alec
authors.initials: HA
authors.lastname: Ross
authors.forename: Jos H
authors.initials: JH
authors.lastname: Thijssen
authors.forename: Brigitte
authors.initials: B
authors.lastname: Toussaint
mesh_terms: D002138:Calibration; D006801:Humans; D007118:Immunoassay / Q000379:methods / Q000592:standards; D013960:Thyroid Function Tests / Q000379:methods* / Q000592:standards*; D013972:Thyrotropin / Q000097:blood*
chemical_list: D013972:Thyrotropin