title: Harmonization and external quality assessment of antithrombin activity assays.
abstract: In the framework of a Dutch project named "Calibration 2000" harmonization of antithrombin activity assays was studied. The commutability of potential calibrators for antithrombin was assessed by means of a twin-study design, which is a multicentre, split-patient sample, between-field-methods protocol. The twin-study consisted of simultaneous analysis of fresh-frozen patient plasmas and three potential calibrators for antithrombin by 30 Dutch laboratories forming 15 couples. The state-of-the-art intralaboratory standard deviation (SD(SA)) was used to assess the commutability of the potential calibrators. The regression line residuals for the potential calibrators were normalized by expressing them as multiples of SD(SA). All residuals of the potential calibrators were within the 3×SD(SA) limit. One potential calibrator was used in an attempt to harmonize antithrombin assay results in a Dutch field study. The interlaboratory coefficient of variation (CV) of the antithrombin results for three test samples could be reduced from 6.9 - 13.2% (before harmonization) to 5.6 - 9.8% using the common calibrator.
  
  
  CONCLUSIONS
  The potential calibrators were commutable. Limited harmonization was achieved by using a common calibrator for all participants.
authors: Department of Thrombosis and Hemostasis, Leiden University Medical Centre, Leiden, The Netherlands. a.m.h.p.van_den_besselaar@lumc.nl
authors: Anton M H P
authors: AM
authors: van den Besselaar
authors: Fred J L M
authors: FJ
authors: Haas
authors: Aldy W H M
authors: AW
authors: Kuypers
mesh_terms: D058833:Antithrombin Proteins / Q000032:analysis* / Q000592:standards*; D001774:Blood Chemical Analysis / Q000592:standards*; D001780:Blood Coagulation Tests / Q000592:standards*; D002138:Calibration / Q000592:standards; D009426:Netherlands; D011785:Quality Assurance, Health Care / Q000592:standards*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
chemical_list: D058833:Antithrombin Proteins