A1C: Recommendations, debates, and questions

Abstract

A1C does reflect the phenomenon of greater hemoglobin glycation at higher mean glycemia and is certainly useful as an objective measure of long-term glycemia in subjects with diabetes. The related concepts that A1C can be used rather than the results of actual patient glucose measurements in accurately ascertaining mean glycemia and that A1C might be useful in the diagnosis of diabetes are therefore highly appealing. One should not, however, expect all subjects to glycate hemoglobin to the same degree for a given level of glycemia, given that a number of lines of evidence indicate that in clinical populations there is heterogeneity in the degree to which this occurs. A1C may not, then, be sufficiently accurate to allow its clinical use in the diagnosis of diabetes in populations of varying age and ethnic background and with illnesses affecting erythrocyte turnover. Moreover, caution appears reasonable before adoption of terminology such as eAG. We need to develop and validate new approaches to understanding glycemic exposure of subjects with diabetes and to develop better approaches to assessment of glycemia among subjects at risk of diabetes. As an example, individuals with increasing fasting glucose when monitored over time appear to be at particularly high risk of developing diabetes (51), and this may be a promising approach to diagnosis. © 2009 by the American Diabetes Association.