Self-monitoring does not improve glycaemic control
Good control of diabetes, measured by achievement of target ranges of glycosylated haemoglobin, has been shown to equate with fewer microvascular complications in both types of diabetes.1,2 It seems probable that glycaemic control also influences macrovascular outcomes.
Until recently it was widely assumed that the increased availability of near-patient measurement of capillary blood glucose would translate into improved management of glycaemia. Unfortunately, the evidence to date suggests that this assumption is wrong. The DiGEM study, published in the British Medical Journal, adds substantially to the evidence that self-monitoring of blood glucose does not improve diabetic control.
The study, based in general practices in Oxfordshire and South Yorkshire, recruited 453 patients with type 2 diabetes. All the patients in the study were aged at least 25 years at diagnosis, managed with diet or oral hypoglycaemic agents, had an HbA1c ? 6.2% at initial assessment and were independent in activities of daily living. None had regularly used a blood glucose meter in the three months before the study.
Participants were randomised to one of three arms: standardised usual care with measurements of HbA1c every three months (the control group); use of a blood glucose meter with advice to contact their doctor for interpretation of results; and use of a blood glucose meter with training in self interpretation and application of the results to lifestyle and treatment.
The primary endpoint of the trial was HbA1c at 12 months. The trial was designed to have a 90% power to detect a difference of 0.5% in HbA1c level. Secondary outcome measures included blood pressure, weight and cholesterol.
The results showed no significant difference in HbA1c between the three groups. Of the secondary endpoints the only significant change was a small decrease in cholesterol in the intensive treatment arms compared with control. The intensively managed groups experienced more hypoglycaemic episodes.
The authors conclude there is no convincing evidence that self-monitoring of blood glucose, with or without instruction, improves glycaemic control in patients with type 2 diabetes not treated with insulin.
The study was very well designed and reported, and could be recommended in its entirety for use by GP trainers and registrars.
The results of this paper are consistent with the Freemantle study, which was reviewed in the March issue of The Practitioner.3,4 This Australian study showed no difference accrued from blood glucose monitoring in a large cross section of patients with diabetes, including those on insulin. An NHS technology assessment drew similar conclusions and there has been guidance towards minimising blood testing in patients with diabetes not treated with insulin.5-7 This is important because the glucose testing strips are expensive – the total cost of glucose testing to the NHS is greater than the cost of oral hypoglycaemic drugs.
Patients or their families often purchase meters in the belief self-monitoring will be helpful. Practices need to have a policy to minimise unnecessary testing.
Farmer A, Wade A, Goyder E et al. Impact of self monitoring of blood glucose in the management of patients with non-insulin treated diabetes: open parallel group randomised trial. BMJ 2007 doi:10.1136/bmj.39247.447431.BEDr Matthew LockyerDr Matthew Lockyer Reviewer
Dr Matthew Lockyer
GP, Suffolk and hospital practitioner in diabetic medicine