Contact the duty biochemist on 0121 3716543 to discuss whether an oral glucose tolerance test (OGTT) is required for a particular patient and/or to book an OGTT. The OGTT is performed at the Diabetes Centre Laboratory in Nuffield House on the QEHB site. In addition, a protocol can be provided for performing an OGTT on wards or in the community.
HbA1c is routinely measured for this purpose. The assay is run daily on weekdays and requires an EDTA plasma sample (purple top). Fructosamine can be used as an alternative when HbA1c is not appropriate. Fructosamine reflects blood glucose over two weeks rather than 2 to 3 months as it reflects glycation of albumin rather than haemoglobin. Fructosamine is performed on serum (yellow or red top) and run daily.
Conventionally diabetes mellitus was diagnosed by high fasting or random blood glucose concentrations, or an abnormal oral glucose tolerance test (OGTT) whilst haemoglobin A1c (HbA1c) was used to monitor longer term glycaemic control in patients with known diabetes mellitus.
In 2011, the World Health Organisation (WHO 2011) recommended that HbA1c measurements should also be used to diagnose diabetes in the majority of asymptomatic individuals, and this recommendation has been agreed in the UK (NHS Diabetes 2011).
An HbA1c of 48 mmol/mol or more is consistent with diabetes. If the patient has no symptoms then a second HbA1c result must be obtained within 2 weeks, and if it remains ≥48 mmol/mol diabetes mellitus is confirmed.
HbA1c values of 42 to 47 mmol/mol suggest a high risk of future diabetes. Such individuals should be offered structured lifestyle education and support to delay/prevent development of diabetes, and have an annual HbA1c test.
HbA1c must be measured in an accredited laboratory undertaking recommended quality assurance procedures. Near patient testing is not appropriate when HbA1c is used for the diagnosis of diabetes.
HbA1c is now the preferred method to diagnose diabetes, except in the following situations where this test would be unreliable, and in whom the traditional methods of diagnosis with blood glucose concentrations remain the method of choice:
Increased red cell turnover
Anaemia (haemoglobin < 80 g/L)
?Type 1 diabetes or acute onset of symptoms of diabetes
Children and adolescents
Patients taking steroids and antipsychotic or other medications that cause a rapid rise in blood glucose
Despite this new approach, if an individual has abnormally high random or fasting blood glucose levels or abnormal OGTT, which would be consistent with diabetes on the traditional criteria, then that patient should be considered to have diabetes irrespective of their HbA1c value. Without symptoms of diabetes two abnormal tests of the same type (two high fasting/random blood glucoses or a diabetic OGTT) are required to confirm diabetes mellitus.
Protection of Personal Information – Clinical Laboratory Services comply with the Trust Data Protection Policy and have procedures in place to allow the Directorate and it’s employees to comply with the Data Protection Act 1998 and associated best practice and guidance.
The Trust Laboratories at Heartlands Hospital, University Hospitals Birmingham, Good Hope Hospital and Solihull Hospital were all hold UKAS (United Kingdom Accreditation Service) accreditation to the internationally recognised ISO 15189 standard For a list of accredited tests and other information please visit the UKAS website. For further test information please visit the test database:
Tests not appearing on appearing on the UKAS scope, are either under consideration or in the process of accreditation and so currently remain outside of our scope of accreditation. However, these tests have been validated to the same high standard as accredited tests and are performed by the same trained and competent staff.
For further information contact Louise Fallon, Quality Manager, 0121 371 5962