Using HbA1c Wisely
Glycated haemoglobin (HbA1c) has been used for monitoring patients with established diabetes for many years but its diagnostic application is a more recent development. This article provides some background to the test, explains dual reporting of results and discusses the use of HbA1c in the diagnosis and monitoring of diabetes.
What is HbA1c?
Adult haemoglobin is predominantly (97% of total) HbA. HbA1c is formed when a glucose molecule non-enzymatically attaches to the N-terminal valine of the β-chain of HbA.
The amount of HbA1c formed is directly proportional to the average plasma glucose concentration during the 120-day life span of the erythrocyte, with recent plasma glucose contributing more than earlier concentrations. HbA1c is therefore a reflection of the average glycaemia over roughly the preceding 6–8 weeks and has a vital role in assessing the risk of an individual developing the complications of diabetes.1
HbA1c for the diagnosis of diabetes mellitus
A 2012 position statement of the Australian Diabetes Society, the Royal College of Pathologists of Australasia (RCPA) and the Australasian Association of Clinical Biochemists (AACB)2 contains the following:
- HbA1c levels ≥6.5% (≥48 mmol/mol) are acceptable for diagnosing diabetes so long as the test is done in a laboratory and no conditions exist ...