Can screening help reduce the burden of diabetes?
Globally, type-2 diabetes is a major public health problem. The International Diabetes Federation estimate that there are 366 million adults currently living with diabetes globally. It is estimated that 35–40% of people in Europe will develop diabetes over their lifetime and diabetes prevalence is increasing rapidly, especially in low to middle income countries. Within the UK it is estimated that around 10% of the NHS budget is spent on diabetes.
Most people are diagnosed with diabetes when they develop symptoms or complications of the disease. However, type 2 diabetes fulfils many of the criteria for screening, with a view to potential early detection and treatment. The disease is common and has a long pre-clinical phase in which it can be readily detected, and in which intervention is possible.
There are several key uncertainties: the magnitude of the benefits of early intervention in people found to be screen positive and the potential harms associated with screening, such as anxiety or adverse effects. The MRC Epidemiology Unit has established a programme of work aimed at reducing these uncertainties and informing public health practice.
Direct quantification of the benefits is difficult in the absence of large scale trials of screening, but public health modelling by the MRC Epidemiology Unit suggests that the benefits may be large. Furthermore, there are key uncertainties that can be addressed by primary research, for example the magnitude of the reduction in risk of cardiovascular disease (CVD) related to intensive management of people with screen detected diabetes.
This question has been addressed through the ADDITION-Europe trial, which was a comparison of an intensive approach to CVD risk management compared to standard care in people found to have diabetes following a step-wise screening programme. Over 30,000 high risk individuals were invited for screening across 343 GP practices in the UK, Netherlands and Denmark. A total of 3,057 people with screen detected diabetes were then randomised to intensive treatment or standard care.
The study showed that screening for type 2 diabetes is feasible in primary care. Overall CVD incidence and mortality was low across both treatment groups, by comparison to populations with known diabetes, which was probably attributable to early detection. Intensive treatment was associated with reduced CVD risk factors. Overall, the benefits of intensive treatment over standard care were small, largely because standard care in this study was so effective. These findings contribute to the public policy discussions about whether and how to screen for diabetes.