Patients with Impaired Glucose Tolerance, Impaired Fasting Glycaemia or a past history of Gestational Diabetes are at particularly high risk of developing Type 2 Diabetes and should be recalled annually for a fasting venous (plasma) glucose measurement.
Other patient groups at high risk of diabetes should be screened opportunistically. These include:
- Subjects from non-Caucasian ethnic groups
- Those with a family history of Type 2 Diabetes
- Those who are obese, in particular with central adiposity (waist 31.5 inches or over for women and 37 inches or over for men)
- Women with polycystic ovarian syndrome
There is little evidence for the effectiveness of screening the general population for diabetes. However, The Joint British Societies guidelines on prevention of cardiovascular disease in clinical practice (JBS 2)** has recommended that all adults aged 40 onwards should have a random (non-fasting) blood glucose as part of an opportunistic risk assessment for cardiovascular disease in primary care.
Screening should preferably be carried out by taking a random venous (plasma) sample for laboratory analysis. If this is normal i.e. < 6mmol/L, then there is no need to repeat for 5 years unless other indications develop. If this > 6.1 mmol/L, but < 11.1 mmol/L, then two further plasma samples (or one if patient is symptomatic) should be taken in line with the diagnostic algorithm for diabetes to confirm or refute a diagnosis. In patients where the first random screening sample is >11.1 mmol/L, only one further sample (preferably fasting) is required.
Urinalysis or capillary blood glucose meter/ test strip analyses are not considered to be accurate screening tools. Abnormal findings using these methods should always be followed up by repeating with a venous (plasma) screening sample, as above. Only when this also shows abnormally high results should further blood glucose measurements be taken, in line with the diagnostic algorithm.
** Heart 2005; 91: 40-45