3 The value of 6.5 % was selected as an optimal cut point for detecting prevalent retinopathy consistent with the definition used for current fasting (≥126 mg/dL) and 2-h (≥200 mg/dL) plasma glucose cut points. The role of the A1c broadened in 2010 when the ADA added A1c ≥6.5 % as a diagnostic criterion for diabetes, allowing the test to be used for both management and diagnosis. 2 Other key studies, such as the United Kingdom Prospective Diabetes Study (UKPDS), have consistently demonstrated the correlation between A1c and diabetes complications and have reinforced currently recommended target values. 1 In 1993, the landmark Diabetes Control and Complications Trial (DCCT) demonstrated its importance as a predictor of diabetes-related outcomes, and the ADA started recommending specific A1c targets in 1994. A1c assays became commercially available in 1978, and the American Diabetes Association (ADA) first recommended using A1c in 1988.

For decades, hemoglobin A1c (A1c) has remained the standard biomarker for glycemic control.