Should we screen for type 2 diabetes? Evaluation against National Screening Committee criteria

The high prevalence of undiagnosed diabetes1 and the proportion of cases with evidence of complications at diagnosis 2 3 undoubtedly create a strong imperative for screening. In the United Kingdom, the National Screening Committee has the task of providing advice about established and newly proposed screening programmes and aims to evaluate these against specified criteria.4 This article evaluates screening for type 2 diabetes in relation to these criteria. #### Summary points Benefits of early detection and treatment of undiagnosed diabetes have not been proved Effectiveness of diabetes screening in reducing cardiovascular disease depends on disease prevalence, background cardiovascular risk, and risk reduction in those screened and treated Disadvantages of screening are important and should be quantified Universal screening is unmerited, but targeted screening in specific subgroups may be justified Clinical management of people with established diabetes should be optimised before a screening programme is considered The first group of issues considered by the National Screening Committee relates to the condition for which screening is proposed. In the case of type 2 diabetes, these issues are relatively uncontroversial. The scale of morbidity and mortality attributable to diabetes is not in question,5 and the longitudinal examination of cohorts has established the overall course of the condition.6 Undiagnosed diabetes is common7; it is not generally characterised by recognised symptoms and is as strongly associated with future risk as diagnosed diabetes.8 Up to 25% of people with diabetes have evidence of microvascular complications at diagnosis, 1 3 and extrapolation of the association between the prevalence of retinopathy and the duration of disease suggests that the true onset of diabetes occurs several years before it is recognised clinically.2 The National Screening Committee's criteria also state that all “cost-effective primary prevention interventions should have been implemented as far as practicable.”4 …