Comparison of HbA1c and OGTT criteria to diagnose diabetes among Chinese.

OBJECTIVE

To examine the sensitivity and specificity of HbA1c testing for the diagnosis of type 2 diabetes in high-risk adults in China and to compare the cardiaovascular risk factors between 2 groups of patients with glycemic status classified by the 2 different tests.

RESEARCH DESIGN AND METHOD

From a cross-sectional survey of prevalence of diabetes in China, we selected adults from the Jinan area of Shandong without known diabetes who underwent OGTT and HbA1c testing on the same day. Cardiovascular risk factors (blood pressure, body mass index, lipid levels) were compared among the subjects divided into 4 groups according to the 2 diabetes diagnostic criteria: true-diabetes, HbA1c-diagnosed diabetes, OGTT-diagnosed diabetes, and nondiabetes.

RESULTS

Among 701 subjects, 65 cases of diabetes were diagnosed by HbA1c ≥6.5% and 94 cases by OGTT. Comparing with OGTT,the sensitivity with level of HbA1c >6.5% was 48.2% and the specificity 97.8%. In total, 30.7% of subjects with HbA1c ≥6.5% were not classified as having diabetes by OGTT criteria, and 52% of subjects with diabetes according to OGTT criteria would be considered nondiabetic by HbA1c recommended criteria. The OGTT- and HbA1c-diabetes groups showed the same cardiovascular risk factors, the levels of which were higher than that for the nondiabetes group.

CONCLUSIONS

We found high specificity and low sensitivity with use of HbA1c level ≥6.5% to diagnose diabetes mellitus. The HbA1c test and OGTT did not reach full concordance. The 2 diagnostic criteria reflect similar levels of cardiovascular risk factors.