The IFCC Reference Measurement System for HbA1c: a 6-year progress report.
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).
Weykamp
Cas
C
Queen Beatrix Hospital, Winterswijk, The Netherlands. c.w.weykamp@skbwinterswijk.nl
John
W Garry
WG
Mosca
Andrea
A
Hoshino
Tadao
T
Little
Randie
R
Jeppsson
Jan-Olof
JO
Goodall
Ian
I
Miedema
Kor
K
Myers
Gary
G
Reinauer
Hans
H
Sacks
David B
DB
Slingerland
Robbert
R
Siebelder
Carla
C
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
D006442:Glycated Hemoglobin; C517652:hemoglobin A1c protein, human