Optimal range of HbA1c for the prediction of future diabetes: A 4-year longitudinal study

AimA glycated hemoglobin (HbA1c) range of 5.7–6.4% has been included as a category of increased risk for diabetes. We evaluated whether or not it is reasonable to apply this HbA1c range to Koreans.MethodsA retrospective analysis was conducted among subjects who participated in comprehensive health check-ups annually for 5 years. A total of 9723 subjects were classified into 12 categories based on the baseline HbA1c level.ResultsDuring 4 years, 601 of the 9723 subjects (6.2%) developed diabetes. Based on ROC analysis, a HbA1c of 5.7% gave an optimal sensitivity of 62% and specificity of 85% to predict diabetes. The point showing a substantial difference in the Kaplan-Meier curves was a HbA1c of 5.7%. The incidence of diabetes was 20.8% among subjects with a baseline HbA1c of 5.7–6.4%. The hazard ratio of developing diabetes was 6.5 (95% CI, 3.7–10.2) in the subjects with a HbA1c of 5.7% compared with the bottom category of HbA1c (<5.0%).ConclusionsA HbA1c cut-point of 5.7% is a suitable value for predicting future diabetes. It is reasonable to consider a HbA1c range of 5.7–6.4% as a category of increased risk for diabetes in Korean, similar to an IFG or IGT.