Should we screen for type 2 diabetes: Yes

Evidence for screening

No trials have compared screening for diabetes with no screening, which would be the ideal platform to establish whether screening is cost effective. The recent ADDITION Europe randomised study of 3055 people investigated the effect of intensive treatment of multiple risk factors in people with screen detected type 2 diabetes. The patients in the control arm were also screen detected but received routine care from primary care practitioners.4 At five year follow-up, the intensive group had significant improvements in cardiovascular risk factors compared with the control group, although the 17% relative risk reduction in the primary outcome (first cardiovascular event) was non-significant (13.5/1000 person years in the intensive treatment group compared with 15.9/1000 in the control group).4 However, the UK Prospective Diabetes Study showed that the effects of tight glycaemic control on development of diabetes related complications are longer term6 and therefore would be unlikely to be seen within the five year follow-up of the ADDITION study. The ACCORD and Veterans Administration diabetes randomised trials also showed benefits of tight control for people without previous cardiovascular events who were earlier in their disease trajectory (duration of diabetes less than 15 years).7 8

In the absence of a control arm without screening, it is difficult to ascertain the true benefits of screening. Current recommendations have therefore been based on modelled cost effectiveness analyses. Any screening programme for diabetes will also identify people at high risk of type 2 diabetes, and the evidence for prevention of diabetes in this group is unequivocal.9 One recent economic decision analysis model estimated that compared with no screening, the cost of screening for diabetes and impaired glucose tolerance followed by lifestyle interventions was £6242 (€7750; $9750) for each quality adjusted life year (QALY) gained.10 A simulated study using the Archimedes model suggested that compared with no screening, screening for type 2 diabetes is cost effective when started between the ages of 30 years and 45 years, with screening repeated every three to five years.11 Compared with no screening, all screening strategies reduced the incidence of myocardial infarction (3-9 events prevented per 1000 people screened) and microvascular complications (3-9 events prevented per 1000 people screened) and deaths (2 to 5 events per 1000 people).11

Practicalities

Another review suggested that two stage screening for diabetes is cost effective for patients aged 40-70 years compared with no screening (£10 216/QALY).12 However, most of the economic modelling studies have used the oral glucose tolerance test for diagnosis, which has been shown to be impractical and reduces uptake.13 Recently the World Health Organization has recommended using glycated haemoglobin (A_1c) concentrations to diagnose diabetes,14 which should increase the uptake of screening.

The recent evidence makes the case for screening for diabetes (and those at high risk) much stronger, and two major initiatives in the UK are likely to help implement screening. The National Health Service Health Checks programme for adults aged 40-74 years was introduced in England in 2009 with the objective of assessing the risk of developing vascular or metabolic disease, including diabetes. The second initiative is the imminent publication of the National Institute for Health and Clinical Excellence’s guidance on identification and prevention of type 2 diabetes in people at high risk.15The guidance makes practical recommendations on risk identification using simple self assessment risk scores or computer based risk scores in people aged 40 to 75 years and younger people from black and minority ethnic groups followed by a fasting glucose or a random haemoglobin A_1c assessment. The guidance also makes pragmatic recommendations to help people make long term lifestyle changes to reduce risk and delay onset of type 2 diabetes.15 The comprehensive modelling in this programme has also suggested that this strategy is likely to be cost effective.

Direct evidence of the benefits of early detection of type 2 diabetes by screening are lacking and are now unlikely to be obtained. However, the ADDITION study, the recent robust modelling studies, and a move to using non-invasive tests followed by haemoglobin A_1c as a diagnostic test for diabetes suggest that screening and intensive risk factor control of people with diabetes is feasible in primary care and is likely to be cost effective.