Haemoglobin A 1c cut-off point to identify a high risk group of future diabetes: Results from the Omiya MA Cohort Study

Abstract

Aims Using the HbA 1c level to define diabetes has several advantages and these advantages also apply to define a high-risk group. However, the risk of diabetes increases as HbA 1c increases and a certain degree of arbitrariness in the cut-off for the high risk group is unavoidable. The aim of this study was to determine the HbA 1c cut-off for defining a high-risk group that corresponds to the fasting plasma glucose cut-off by comparing the risk of diabetes against the fasting plasma glucose and HbA 1c levels in the Japanese population. Methods A retrospective cohort study was conducted using data from annual health examinations performed in Omiya city. A total of 11271 subjects between the ages of 40 and 79years without diabetes at baseline were followed for up to 7years. According to the new diagnostic criteria, diabetes was defined as an fasting plasma glucose level ≥7mmol/l or an HbA 1c level ≥48mmol/mol (≥6.5%) or a self-report. The HbA 1c cut-off corresponding to the fasting plasma glucose cut-off was determined using the incidence, hazard ratio, and a receiver operating characteristic analysis. Results Eight hundred and sixty subjects developed diabetes. The incidence, hazard ratio, and receiver operating characteristic analysis all indicated that an HbA 1c cut-off of 39mmol/mol (5.7%) corresponded to an fasting plasma glucose level of 5.6mmol/l. Conclusions Our results suggested that the HbA 1c cut-off for high-risk of diabetes should be 39mmol/mol (5.7%), consistent with the American Diabetes Association recommendation. Further research is needed to determine whether our results are applicable to other populations. © 2012 The Authors. Diabetic Medicine © 2012 Diabetes UK.