Japanese standard reference material JDS Lot 2 for haemoglobin A1c. II: Present state of standardization of haemoglobin A1c in Japan using the new reference material in routine clinical assays

BACKGROUND: In 2001, the Committee on Standardization of Laboratory Testing Related to Diabetes Mellitus of the Japan Diabetes Society (JDS) prepared and certified a new reference material for haemoglobin A1c (HbA1c), Lot 2. The standardization programme for HbA1c measurement in Japan is currently based on Lot 2, although some laboratories still use the previous material (Lot 1). The values assigned to Lot 2 were based on the consensus values for Lot 1 and should give the same results. Therefore, there should be no difference in the measured values no matter which calibrators are used. The Committee conducted a domestic survey in order to confirm this relationship. METHOD: In November 2002, four samples for HbA1c assay were sent to 795 laboratories as part of a national survey in Japan. Assays were performed using the laboratories' routine clinical methods. The coefficients of variation (CVs) of the reported values from all laboratories for the samples were calculated in order to determine the current level of standardization in Japan. RESULTS: The overall CVs in the measured values for the four samples ranged from 2.7% to 4.0%. Values from laboratories using calibrators based on Lots 1 and 2 were similar. CONCLUSION: The present state of standardization for the routine measurement of HbA1c in Japan, as indicated by the 2002 survey, is excellent. This should aid in the eventual conversion of Lot 2 to IFCC-based values from the results of the 2002 national HbA1c survey.