title: The IFCC Reference Measurement System for HbA1c: a 6-year progress report.
abstract: BACKGROUND
  The IFCC Reference Measurement System for hemoglobin (Hb)A(1c) (IFCC-RM) has been developed within the framework of metrologic traceability and is embedded in a network of 14 reference laboratories. This paper describes the outcome of 12 intercomparison studies (periodic evaluations to control essential elements of the IFCC-RM).
  
  
  METHODS
  Each study included: unknown samples (to test individual network laboratories); known samples (controls); recently manufactured calibrators (to check calculated assigned value); stored calibrators (to test stability) and a calibration-set (to calibrate the IFCC-RM). The unknown samples are measured by use of the IFCC-RM and the designated comparison methods [DCMs; the National Glycohemoglobin Standardization Program (NGSP) in the US, Japanese Diabetes Society/Japanese Society for Clinical Chemistry (JDS/JSCC) in Japan, and Mono-S in Sweden] are used to investigate the stability of the Master Equation (ME), the relationship between IFCC-RM and DCMs.
  
  
  RESULTS
  A total of 105 IFCC-RM data sets were evaluated: 95 were approved, 5 were not, and for 5 no data were submitted. Trend analysis of the MEs, expressed as change in percentage HbA(1c) per year, revealed 0.000% (NGSP, not significant), -0.030%, (JDS/JSCC; significant) and -0.016% (Mono-S; not significant). Evaluation of long-term performance revealed no systematic change over time; 2 laboratories showed significant bias, 1 poor reproducibility. The mean HbA(1c) determined by laboratories performing mass spectrometry (MS) was the same as the mean determined by laboratories using capillary electrophoresis (CE), but the reproducibility at laboratories using CE was better. One batch of new calibrators was not approved. All stored calibrators were stable.
  
  
  CONCLUSIONS
  A sound reference system is in place to ensure continuity and stability of the analytical anchor for HbA(1c).
authors.affiliation: Queen Beatrix Hospital, Winterswijk, The Netherlands. c.w.weykamp@skbwinterswijk.nl
authors.forename: Cas
authors.initials: C
authors.lastname: Weykamp
authors.forename: W Garry
authors.initials: WG
authors.lastname: John
authors.forename: Andrea
authors.initials: A
authors.lastname: Mosca
authors.forename: Tadao
authors.initials: T
authors.lastname: Hoshino
authors.forename: Randie
authors.initials: R
authors.lastname: Little
authors.forename: Jan-Olof
authors.initials: JO
authors.lastname: Jeppsson
authors.forename: Ian
authors.initials: I
authors.lastname: Goodall
authors.forename: Kor
authors.initials: K
authors.lastname: Miedema
authors.forename: Gary
authors.initials: G
authors.lastname: Myers
authors.forename: Hans
authors.initials: H
authors.lastname: Reinauer
authors.forename: David B
authors.initials: DB
authors.lastname: Sacks
authors.forename: Robbert
authors.initials: R
authors.lastname: Slingerland
authors.forename: Carla
authors.initials: C
authors.lastname: Siebelder
mesh_terms: D015982:Bias; D002138:Calibration; D002851:Chromatography, High Pressure Liquid; D019963:Clinical Chemistry Tests / Q000592:standards*; D019075:Electrophoresis, Capillary; D006442:Glycated Hemoglobin / Q000032:analysis / Q000592:standards*; D006801:Humans; D016014:Linear Models; D013058:Mass Spectrometry; D011786:Quality Control; D012015:Reference Standards; D015203:Reproducibility of Results; D035501:Uncertainty
chemical_list: D006442:Glycated Hemoglobin; C517652:hemoglobin A1c protein, human