Objective: A1C > or =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: In the Insulin Resistance Atherosclerosis Study, 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)).
Results: Participants with A1C > or =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 individuals with DM(FPG126), mean, median, and interquartile range of A1C were 7.0, 6.6, and 6.0-7.1%.
Conclusions: A1C > or =6.5% identifies fewer individuals than DM(1999WHO) or DM(FPG126). Studies are needed to determine that A1C > or =6.5% compromises neither blood pressure and lipid management in early diabetes nor the implementation of lifestyle interventions for diabetes prevention.