The high rates of abnormal fasting and postchallenge glucose found in NHANES III, together with the increasing frequency of obesity and sedentary lifestyles in the population, make it likely that diabetes will continue to be a major health problem in the U.S.

OBJECTIVE -To define the relationship between HbA 1c and plasma glucose (PG) levels in patients with type 1 diabetes using data from the Diabetes Control and Complications Trial (DCCT).RESEARCH DESIGN AND METHODS -The DCCT was a multicenter, randomized clinical trial designed to compare intensive and conventional therapies and their relative effects on the development and progression of diabetic complications in patients with type 1 diabetes. Quarterly HbA 1c and corresponding seven-point capillary blood glucose profiles (premeal, postmeal, and bedtime) obtained in the DCCT were analyzed to define the relationship between HbA 1c and PG. Only data from complete profiles with corresponding HbA 1c were used (n ϭ 26,056). Of the 1,441 subjects who participated in the study, 2 were excluded due to missing data. Mean plasma glucose (MPG) was estimated by multiplying capillary blood glucose by 1.11. Linear regression analysis weighted by the number of observations per subject was used to correlate MPG and HbA 1c . CONCLUSIONS -We have defined the relationship between HbA 1c and PG as assessed in the DCCT. Knowing this relationship can help patients with diabetes and their healthcare providers set day-to-day targets for PG to achieve specific HbA 1c goals. RESULTS Diabetes Care 25:275-278, 2002

Background: The national programs for the harmonization of hemoglobin (Hb)A1c measurements in the US [National Glycohemoglobin Standardization Program (NGSP)], Japan [Japanese Diabetes Society (JDS)/Japanese Society of Clinical Chemistry (JSCC)], and Sweden are based on different designated comparison methods (DCMs). The future basis for international standardization 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 performed in 2001–2003. In each study five to eight pooled blood samples were measured by 11 reference laboratories of the IFCC Network of Reference Laboratories, 9 Secondary Reference Laboratories of the NGSP, 3 reference laboratories of the JDS/JSCC program, and a Swedish reference laboratory. Regression equations were determined for the relationship between the IFCC RM and each of the DCMs. Results: Significant differences were observed between the HbA1c results of the IFCC RM and those of the DCMs. Significant differences were also demonstrated between the three DCMs. However, in all cases the relationship of the DCMs with the RM were linear. There were no statistically significant differences between the regression equations calculated for each of the four studies; therefore, the results could be combined. The relationship is described by the following regression equations: NGSP-HbA1c = 0.915(IFCC-HbA1c) + 2.15% (r2 = 0.998); JDS/JSCC-HbA1c = 0.927(IFCC-HbA1c) + 1.73% (r2 = 0.997); Swedish-HbA1c = 0.989(IFCC-HbA1c) + 0.88% (r2 = 0.996). Conclusion: There is a firm and reproducible link between the IFCC RM and DCM HbA1c values.

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Glycosylated hemoglobin measurement has been shown to be a potentially useful tool for both a variety of research applications and for the management of patients with diabetes mellitus. None of the methods available to quantitate glycosylated hemoglobins is ideal. We have reviewed a number of critical methodologie considerations for Chromatographie procedures including the effects of sample storage under various conditions, and the importance of removing labile components prior to analyses. We have developed a method for the colorimetrie determination of glycosylated hemoglobins that is more rapid than methods reported previously, that correlates well with results using high-performance liquid chromatogra-phy, and that can he standardized between laboratories. We have reviewed our experience using glycosylated hemoglobin in a large population of diabetic youths. We have presented a method for developing realistic goals for glucose control using glycosylated hemoglobin and for using glycosylated hemoglobin as a patient education and care reinforcement tool.