title: Harmonization of measurement results of the alcohol biomarker carbohydrate-deficient transferrin by use of the toolbox of technical procedures of the International Consortium for Harmonization of Clinical Laboratory Results.
abstract: BACKGROUND
  The need for equivalent results of routine measurement procedures for the alcohol biomarker carbohydrate-deficient transferrin (CDT) has been recognized by the IFCC. This article describes a project to harmonize CDT as conducted by an IFCC working group initiated for this purpose.
  
  
  METHODS
  We used procedures for achieving harmonization as developed by the Consortium for Harmonization of Clinical Laboratory Results to assess the suitability of a candidate reference measurement procedure (cRMP), candidate reference materials (cRMs), and the success of efforts to achieve harmonization.
  
  
  RESULTS
  CDT measurement procedures in routine use showed good reproducibility (CV 1.1%-2.8%) and linearity (r > 0.990) with variable slopes (0.766-1.065) and intercepts (-0.34 to 0.92) compared to the cRMP. Heterogeneity after simulated harmonization was 4.7%. cRMs of frozen human native sera demonstrated commutability and 3-year stability for routine measurement procedures. The cRMP provided reproducible value assignment to cRMs with an expanded uncertainty (k = 2) of 0.03% at the 1.2% CDT level and 0.06% at the 4.4% CDT level. Harmonization efforts reduced the intermeasurement CV from 8.8% to 3.4%, allowed 99% recovery of the values assigned with the cRMP, and demonstrated 99% of results within the desirable allowable total error. Harmonization was less successful in samples with low CDT and high trisialotransferrin concentrations.
  
  
  CONCLUSIONS
  Harmonization of CDT is possible with frozen human native sera as cRMs with values assigned by use of the cRMP. We propose the cRMP as a candidate international conventional reference measurement procedure and cRMs as candidate international calibrators.
authors.affiliation: Department of Clinical Chemistry, Queen Beatrix Hospital, Winterswijk, the Netherlands; c.w.weykamp@skbwinterswijk.nl.
authors.forename: Cas
authors.initials: C
authors.lastname: Weykamp
authors.affiliation: Department of Clinical Chemistry, Meander Medical Center, Amersfoort, the Netherlands;
authors.forename: Jos
authors.initials: J
authors.lastname: Wielders
authors.affiliation: Department of Laboratory Medicine, Karolinska Institutet, and Karolinska University Laboratory, Clinical Chemistry, Stockholm, Sweden;
authors.forename: Anders
authors.initials: A
authors.lastname: Helander
authors.affiliation: The Center for Drug and Alcohol Programs, Medical University of South Carolina, Charleston, SC;
authors.forename: Raymond F
authors.initials: RF
authors.lastname: Anton
authors.affiliation: Toxicology Reference Laboratory, SS. Antonio e Biagio Hospital, Alessandria, Italy;
authors.forename: Vincenza
authors.initials: V
authors.lastname: Bianchi
authors.affiliation: Department of Laboratory Medicine, Malmö University Hospital, Malmö, Sweden;
authors.forename: Jan-Olof
authors.initials: JO
authors.lastname: Jeppsson
authors.affiliation: Department of Clinical Chemistry, Queen Beatrix Hospital, Winterswijk, the Netherlands;
authors.forename: Carla
authors.initials: C
authors.lastname: Siebelder
authors.affiliation: Queensland Institute of Medical Research, Brisbane, Australia;
authors.forename: John B
authors.initials: JB
authors.lastname: Whitfield
authors.affiliation: Laboratoire de Biochimie, Hôpital Trousseau, Tours, France.
authors.forename: François
authors.initials: F
authors.lastname: Schellenberg
mesh_terms: D000428:Alcohol Drinking / Q000097:blood*; D015415:Biomarkers / Q000097:blood; D002851:Chromatography, High Pressure Liquid; D019075:Electrophoresis, Capillary; D006801:Humans; D007118:Immunoassay; D009391:Nephelometry and Turbidimetry; D012015:Reference Standards; D012016:Reference Values; D014168:Transferrin / Q000031:analogs & derivatives* / Q000032:analysis / Q000592:standards
chemical_list: D015415:Biomarkers; D014168:Transferrin; C056759:carbohydrate-deficient transferrin