Screen and intervene to prevent diabetes?

The BMJ includes a review of screening tests for non-diabetic hyperglycaemia (“pre-diabetes” is unsatisfactory because many people so labelled do not develop diabetes) and of interventions to reduce or delay progression to type 2 diabetes. If we screen for diabetes, we may, depending on test and cut-offs used, identify more people with impaired glucose tolerance and impaired fasting glucose (the two forms of non-diabetic hyperglycaemia) than with diabetes. Screening for impaired glucose tolerance, however, meets most, but not all, of the National Screening Committee criteria.1

In their study, Barry and colleagues2 conclude that there is no perfect screening test for non-diabetic hyperglycaemia. They report that glycated haemoglobin (HbA_1c) is only about 50% sensitive, but the review does not provide sensitivities for a range of thresholds. HbA_1c could be 100% sensitive if a low enough threshold was chosen, but at the cost of substantially more false positives. In screening, there is usually a trade-off between sensitivity and specificity. The researchers found that fasting …