The ADDITION study (Anglo-Danish-Dutch Study of Intensive Treatment In People with Screen Detected Diabetes in Primary Care) was planned in 1999 to evaluate whether population based screening for undiagnosed type 2 diabetes was feasible in a primary care setting, whether subsequent optimised intensive treatment of diabetes, and associated risk factors, among screen-detected patients was feasible in primary care and benefitted patients, and to quantify the harms associated with screening. Previous screening studies have focused on people with prediabetes and how to prevent progression from prediabetes to diabetes.
Type 2 diabetes fulfils many of the criteria for screening. It is a common chronic disease affecting 350 million people worldwide in 2011 and predicted to reach 550 by 2030. A significant proportion of people with diabetes, up to 50% in many studies, remain undiagnosed and therefore untreated. Expenditure related to diabetes in 2010 was estimated to be approximately 10% of total healthcare budgets, and is projected to rise to 17% in 2035.
Raised cardiovascular risk among people with diabetes
People with diabetes have raised cardiovascular risk and up to 50% exhibit evidence of micro- or macro-vascular complications at diagnosis. Complications of diabetes are associated with reduced life expectancy and quality of life. Intensive treatment of single and multiple risk factors (elevated glucose, lipids and blood pressure) has been shown to reduce the risk of developing micro- and macro-vascular complications in people with clinically diagnosed type 2 diabetes.
The target population for the screening program was close to 400.000 people aged 40-69 years. The screening program differed between countries and formed different at risk groups with impaired fasting blood glucose, impaired glucose tolerance or increased cardiovascular disease risk without dysglycemia.
Based on these observations screening for diabetes has been recommended in several countries in line with conclusions from a modelling study. This is in spite of the lack of direct evidence from randomized controlled trials and the remaining uncertainty concerning the magnitude of the benefit of treatment in the lead time between detection by screening and clinical diagnosis, the magnitude of the direct and indirect harms associated with screening and the absence of data on overall cost-effectiveness of screening programmes.