Performance of glycated haemoglobin (HbA1c) as a screening test for diabetes and impaired glucose tolerance (IGT) in a high risk population—The Brazilian Xavante Indians

Abstract Aims To examine the properties of HbA1c to detect diabetes and IGT in adult Brazilian Xavante Indians, a high risk population for diabetes. Methods The survey was carried out between October 2010 and January 2012 and based on a 75 g oral glucose tolerance test (OGTT). Basal and 2 h capillary glycaemia were measured by HemoCue Glucose 201+; HbA1c using an automated high-performance liquid chromatography analyzer (Tosoh G7). Results 630 individuals aged ≥20 years were examined and 80 had a previous diagnosis of diabetes. Sensitivity, specificity and accuracy for HbA1c ≥ 6.5% (≥48 mmol/mol) were 71.3%, 90.5% and 87.2%. The areas under the ROC curve (AUC) was 0.88 (95%CI: 0.83–0.93). To identify IGT, HbA1c values between 5.7% and 6.4% (39–47 mmol/mol) presented sensitivity, specificity and accuracy of 87.2%, 24.7% and 51.4%, with an AUC of 0.62 (95%CI: 0.57–0.67). Conclusions The ADA/WHO proposed cut-off of 6.5% (48 mmol/mol) for HbA1c was adequate to detect diabetes among the Xavante. However, the performance of the ADA proposed cut-off points for pre-diabetes, when used to detect IGT was inadequate and should not be recommended.