Use of HbA_1c in the diagnosis of diabetes

Before 2010, guidelines recommended the measurement of blood glucose for diagnosing diabetes. Improved standardisation in the measurement of glycated haemoglobin (HbA_1c) and wider availability of the assay led to a recommendation in 2011 by the World Health Organization that HbA_1c should be used instead.1 This recommendation was included within a recent UK public health guidance for the identification of people at high risk of diabetes.2 In addition, a UK expert advisory body convened by the Department of Health has—after an extended period of consultation—now stated how the WHO recommendations should be implemented.3

The expert advisory group recommends that an HbA_1c cut-off point of 48 mmol/mol or more (6.5%) be used for the diagnosis of diabetes. Unless the clinical diagnosis is clear, a second confirmatory measurement is needed as soon as possible. If either the initial or follow-up measurement is less than 48 mmol/mol, the diagnosis of diabetes should not be made.3 The group recommended that patients with an HbA_1c of 42-47 mmol/mol should be considered at high risk of diabetes and provided with intensive lifestyle advice and retested annually. Those with an HbA_1c of less than 42 mmol/mol may still have a high risk of diabetes and should be treated according to clinical indication, with retesting at least …