Blood Tests Exclude Impaired Glucose Tolerance

Two blood tests have been compared that could aid in the diagnosis of impaired glucose tolerance in high-risk individuals.

The two tests were the glycated hemoglobin (HbA1c) test, and the oral glucose tolerance test (OGTT) whereby the blood is drawn before the patient drinks a standard glucose solution, and afterwards at various intervals for up to two hours.

In a study carried out at the Virgen Macarena University Hospital (Seville, Spain), 713 patients with at least two risk factors for the development of type 2 diabetes were enrolled in the study. Fasting glucose and HbA1c were measured in all individuals. Patients whose fasting glucose concentrations were below 7.0 mmol/L underwent an OGTT.

From the study, it was found that 234 patients were euglycemic and had a normal blood glucose level, 200 had impaired fasting glucose, 118 presented with impaired glucose tolerance and 161 met the diagnostic criteria for type 2 diabetes. The glucose tolerance test was performed in 596 patients (83.6%). Statistically significant differences were observed for HbA1c concentrations in all groups.

Receiver operating characteristic curve analysis was performed to assess the capability of HbA1c to discriminate between normal glucose tolerance and impaired glucose tolerance. An HbA1c 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.

The authors concluded that HbA1c can be used to rule outpatients at high-risk of developing type 2 diabetes. The study was published in December 2010 in Clinical Chemistry and Laboratory Medicine.

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Virgen Macarena University Hospital