Guidance on HbA1C for diagnosis

Type 2 diabetes

6 Aug 2015

New guidelines on the use of HbA1c for diagnosing diabetes aims to educate practitioners on its benefits and limitations.

The guidelines endorsed by the Australian Diabetes Society, Royal College of Pathologists of Australasia and the Australasian Association of Clinical Biochemists notes that if used appropriately HbA1c assessment should provide a cost-effective, efficient and simple tool for the early diagnosis of type 2 diabetes.

However it was important that medical practitioners who elect to use the test for diagnostic purposes understand its nature, its limitations and its benefits, state the guidelines which are published in the MJA.

Specifically, the guidance recommends that:

  • HbA1c assessment should be considered in asymptomatic patients at high risk of developing diabetes (AUSDRISK score ≥ 12 or pre-existing medical condition or ethnic background associated with high rates of type 2 diabetes).
  • If one or more diabetes symptoms are present in a patient at low risk, blood glucose levels should be used for diagnosis.
  • Patients who have multiple symptoms suggestive of diabetes mellitus are not asymptomatic, and their blood glucose levels should be assessed.
  • An HbA1c level ≥ 48 mmol/mol (6.5%) suggests that the patient has diabetes mellitus.
  • An HbA1c level < 48 mmol/mol (6.5%) suggests that the patient does not have diabetes mellitus. As the test has been performed in a high-risk patient, the test should be repeated 12 months later.
  • A confirmatory test should be performed on another day, ideally as soon as possible and before any lifestyle or pharmacological interventions are commenced.
  • Be aware of conditions that may invalidate the test results such as increased erythropoiesis, abnormal haemoglobin or reduced glycation.

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