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

Abstract

Aim: A 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.

Methods: A 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.

Results: During 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%).

Conclusions: A 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.