A 54-year-old woman with suspected diabetes mellitus has an oral glucose tolerance test, following the standard WHO protocol. The following results are obtained:
How should these results be interpreted?
1.Impaired fasting glucose and impaired glucose tolerance
4.Impaired glucose tolerance
5.Impaired fasting glucose
The following is based on the World Health Organisation (WHO) 2006 guidelines.
If the patient is symptomatic:
fasting glucose greater than or equal to 7.0 mmol/l
random glucose greater than or equal to 11.1 mmol/l (or after 75g oral glucose tolerance test)
If the patient is asymptomatic the above criteria apply but must be demonstrated on two separate occasions.
In 2011 WHO released supplementary guidance on the use of HbA1c on the diagnosis of diabetes:
a HbA1c of greater than or equal to 6.5% (48 mmol/mol) is diagnostic of diabetes mellitus
a HbAlc value of less than 6.5% does not exclude diabetes (i.e. it is not as sensitive as fasting samples for detecting diabetes)
in patients without symptoms, the test must be repeated to confirm the diagnosis
it should be remembered that misleading HbA1c results can be caused by increased red cell turnover (for example anaemia, haemoglobinopathies and pregnancy)
Impaired fasting glucose and impaired glucose tolerance
A fasting glucose greater than or equal to 6.1 but less than 7.0 mmol/l implies impaired fasting glucose (IFG)
Impaired glucose tolerance (IGT) is defined as fasting plasma glucose less than 7.0 mmol/l and OGTT 2-hour value greater than or equal to 7.8 mmol/l but less than 11.1 mmol/l