Statistical methods for monitoring the relationship between the IFCC reference measurement procedure for hemoglobin A1c and the designated comparison methods in the United States, Japan, and Sweden.
BACKGROUND
The American Diabetes Association (ADA)/European Association for the Study of Diabetes (EASD)/International Diabetes Federation (IDF)/IFCC Consensus Statement on the worldwide standardization of HbA(1c) states that "... [HbA(1c)] results are to be reported world-wide in IFCC units ... and derived NGSP units ... , using the IFCC-NGSP master equation."


METHODS
We describe statistical methods to evaluate and monitor the relationships as expressed in master equations (MEs) between the IFCC Reference Measurement procedure (IFCC-RM) and designated comparison methods (DCMs) [US National Glycohemoglobin Standardization Program (NGSP), Japanese Diabetes Society/Japanese Society for Clinical Chemistry (JDS/JSCC), and Mono-S in Sweden]. We applied these statistics, including uncertainty calculations, to 12 studies in which networks of reference laboratories participated, operating the IFCC-RM and DCMs.


RESULTS
For NGSP and Mono-S, slope, intercept, and derived percentage HbA(1c) at the therapeutic target show compliance with the respective MEs in all 12 studies. For JDS/JSCC, a slight deviation is seen in slope and derived percentage HbA(1c) in 2 of the 12 studies. Using the MEs, the uncertainty in an assigned value increases from 0.42 mmol/mol HbA(1c) (IFCC-RM) to 0.47 (NGSP), 0.49 (JDS/JSCC), and 0.51 (Mono-S).


CONCLUSIONS
We describe sound statistical methods for the investigation of relations between networks of reference laboratories. Application of these statistical methods to the relationship between the IFCC-RM and DCMs in the US, Japan, and Sweden shows that they are suitable for the purpose, and the results support the applicability of the ADA/EASD/IDF/IFCC Consensus Statement on HbA1c measurement.
Roche Diagnostics GmbH, Department of Biostatistics, Penzberg, Germany.
Andrea
A
Geistanger
Sabine
S
Arends
Christoph
C
Berding
Tadao
T
Hoshino
Jan-Olof
JO
Jeppsson
Randie
R
Little
Carla
C
Siebelder
Cas
C
Weykamp
D019963:Clinical Chemistry Tests / Q000379:methods / Q000592:standards / Q000706:statistics & numerical data*; D003627:Data Interpretation, Statistical; D003920:Diabetes Mellitus / Q000097:blood*; D006442:Glycated Hemoglobin / Q000032:analysis*; D006801:Humans; D007564:Japan; D009313:National Health Programs; D017410:Practice Guidelines as Topic; D012015:Reference Standards; D013548:Sweden; D035501:Uncertainty; D014481:United States
D006442:Glycated Hemoglobin; C517652:hemoglobin A1c protein, human