Glycated hemoglobin vs. the oral glucose tolerance test for the exclusion of impaired glucose tolerance in high-risk individuals

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 out patients at high-risk of developing type 2 diabetes.