Abstract

Objective: Hemoglobin A1c (A1C) ≥6.5% has been recently proposed as the defining criterion for diabetes. However, performance characteristics of this definition have not been described.

Research Design and Methods: We compared new to previous definitions of diabetes, 1999 World Health Organization (DM_1999WHO) and 2003 American Diabetes Association based on fasting glucose alone (DM_FPG126), in the Insulin Resistance Atherosclerosis Study.

Results: Participants with A1C ≥6.5%, DM_1999WHO, and DM_FPG126 were 44 (5.2%), 132 (15.4%), and 61 (7.1%), respectively. In individuals with DM_1999WHO, mean, median, and interquartile range of A1C were 6.3%, 5.9%, and 5.5 – 6.6%, respectively; in those with DM_FPG126, 7.0%, 6.6%, and 6.0 – 7.1%.

Conclusions: A1C ≥6.5% identifies fewer individuals than DM_1999WHO or DM_FPG126. Studies are needed to determine that A1C ≥6.5% compromises neither blood pressure and lipid management in early diabetes nor the implementation of lifestyle interventions for diabetes prevention.