Practice Rational Testing

Using haemoglobin A1c to diagnose type 2 diabetes or to identify people at high risk of diabetes

BMJ 2014; 348 doi: https://doi.org/10.1136/bmj.g2867 (Published 25 April 2014) Cite this as: BMJ 2014;348:g2867
  1. Eric S Kilpatrick, honorary professor1,
  2. Stephen L Atkin, professor of medicine2
  1. 1Department of Clinical Biochemistry, Hull Royal Infirmary and Hull York Medical School, Hull HU3 2JZ, UK
  2. 2Weill Cornell Medical College Qatar, Doha, Qatar
  1. Correspondence to: E S Kilpatrick Eric.Kilpatrick{at}hey.nhs.uk
  • Accepted 2 April 2014

Learning points

  • Haemoglobin A1c (HbA1c) can now be used as an alternative test to glucose concentration for diagnosing type 2 diabetes or identifying people at high risk of developing the disease

  • Be aware of the conditions in which use of HbA1c would be inappropriate, including suspected type 1 diabetes, pregnancy, acute medical illness, and kidney failure

  • Also be mindful of conditions that might affect HbA1c, such as abnormal haemoglobins and anaemia

  • Do not routinely test both glucose and HbA1c in the same patient

A 48 year old man presented to his general practitioner with a 12 month history of fatigue (which he put down to long office hours) and with urinary frequency. He had no previous health problems, his blood pressure was 145/85 mm Hg, and his body mass index was 29. His father had developed type 2 diabetes at the age of 65 years, and his paternal grandmother had been found to have diabetes at the age of about 60 following the development of a gangrenous toe. The patient’s dipstick urine test showed no glycosuria, ketonuria, proteinuria, blood, leucocytes, or nitrites.

What is the next investigation?

All the possible causes of fatigue should be considered,1 but given the patient’s symptoms and his risk factors for developing type 2 diabetes, including family history and being overweight, a diagnosis of diabetes certainly needs to be excluded. Tests for diabetes are used to evaluate both patients with symptoms (as in this case) and asymptomatic patients who have been identified by a validated risk assessment tool as being at high risk of developing type 2 diabetes.2

Using glucose to diagnose diabetes

Since the early 20th century, the diagnosis of diabetes has been based on the measurement of glucose concentrations in the blood. This usually takes the form of laboratory measured fasting plasma glucose concentration and, when indicated, …

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