behalf of the IFCC Working Group on HbA1c Standardization Background: The national programs for the harmoni-

are based on different designated comparison methods (DCMs). The future basis for international standardiza-tion will be the reference system developed by the IFCC Working Group on HbA1c Standardization. The aim of the present study was to determine the relationships between the IFCC Reference Method (RM) and the DCMs. Methods: Four method-comparison studies were per-formed in 2001–2003. In each study five to eight pooled blood samples were measured by 11 reference laborato-ries of the IFCC Network of Reference Laboratories, 9 Secondary Reference Laboratories of the NGSP, 3 refer-ence laboratories of the JDS/JSCC program, and a Swed-ish reference laboratory. Regression equations were determined for the relationship between the IFCC RM and each of the DCMs