Abstract

Background: The aim of this study was to compare the use of glycated hemoglobin (HbA_1c) and the oral glucose tolerance test (OGTT) in the diagnosis of impaired glucose tolerance in high-risk individuals.

Methods: A total of 713 patients with at least two risk factors for the development of type 2 diabetes were enrolled in the study. Fasting glucose and HbA_1c were measured in all individuals. Patients whose fasting glucose concentrations were below 7.0 mmol/L underwent an OGTT.

Results: From the 713 patients, 234 were euglycemic, 200 had impaired fasting glucose, 118 presented with impaired glucose tolerance and 161 met the diagnostic criteria for type 2 diabetes. OGTT was performed in a total of 596 patients (83.6%). Statistically significant differences were observed for HbA_1c concentrations in all groups. Receiver operating characteristic curve analysis was performed to assess the capability of HbA_1c to discriminate between normal glucose tolerance and impaired glucose tolerance. An HbA_1c value of 36 mmol/mol (5.4%) gave an optimal sensitivity of 85% and a specificity of 73%, and a negative predictive value of 97% for identifying patients with impaired glucose tolerance.

Conclusions: HbA_1c can be used to rule outpatients at high-risk of developing type 2 diabetes.

Clin Chem Lab Med 2010;48:1719–22.