Correlation of A1C with Average Glucose (AG)
Table 8, as shown on this slide, contains the correlation between A1C levels and mean plasma glucose (PG) levels based on data from the international A1C-Derived Average Glucose (ADAG) trial using frequent SMBG and continuous glucose monitoring (CGM) in 507 adults (83% Caucasian) with type 1, type 2, and no diabetes1 The ADA and the American Association of Clinical Chemistry have determined that the correlation (r = 0.92) is strong enough to justify reporting both an A1C result and an estimated average glucose (eAG) results when a clinician orders the A1C test2 A calculator for converting A1C results into eAG, in either mg/dL or mmol/L, is available at http://professional.diabetes.org/eAG For patients in whom A1C/eAG and measured blood glucose appear discrepant, clinicians should consider the possibilities of hemoglobinopathy or altered red cell turnover, and the options of more frequent and/or different timing of SMBG or use of CGM Other measures of chronic glycemia, such as fructosamine, are available, but their linkage to average glucose and their prognostic significance are not as clear as is the case for A1C38References Nathan DM, Kuenen J, Borg R, et al for the A1C-Derived Average Glucose Study Group. Translating the A1C assay into estimated average glucose values. Diabetes Care 2008;31:1473-1478. American Diabetes Association. Standards of medical care in diabetes—2013. Diabetes Care 2013;36(suppl 1):S19; Table 8.