Screening: the programme

"There should be evidence from high quality Randomised Controlled Trials that the screening programme is effective in reducing mortality or morbidity".

Modelling studies suggest that a programme of screening for diabetes would reduce both diabetes-related and overall mortality[1]. However, results from a pragmatic, parallel-group, cluster-randomised trial of 33 general practices in eastern England (ADDITION-Cambridge) found that screening for type 2 diabetes in those at high risk did not result in a reduction in all-cause, cardiovascular, or diabetes-related mortality over 10 years [2]. In an extension to the ADDITION-Cambridge study, a sub-group of the trial cohort were sent a questionnaire asking about their health status seven years after the initial invitation to take part in the screening programme. There were no significant differences between the screening and control groups in the proportion of participants reporting angina, heart attack and stroke, self-rated health, total physical activity, current smoking and alcohol consumption [3]. Taken together, these results suggest that screening for type 2 diabetes appears to have limited long-term impact on population levels of mortality, cardiovascular morbidity, self-rated health and health behaviour. Results from the treatment phase of the ADDITION-Europe study suggest that there are likely to be benefits for those found with detectable disease [4]but the overall benefits of screening might be smaller than expected. This critical screening criterion has therefore not been satisfied.

"There should be evidence that the complete screening programme (test, diagnostic procedures, treatment/ intervention) is clinically, socially and ethically acceptable to health professionals and the public".

The ADDITION-Cambridge study suggests that it is feasible and acceptable to primary care staff and patients to screen for type 2 diabetes in general practice using a risk score to select a high-risk population and capillary glucose measurement as the initial screening test for diabetes [5]. Qualitative analysis of interviews with staff in six practices participating in the ADDITION-Cambridge study showed that primary care teams implemented the screening programme differently [6]. Staff felt that patients accepted the screening and subsequent management as any other clinical activity but emphasised that screening is ‘more than measurement’. Screening required individual explanations, advice on health-related behaviours and appropriate follow-up. Similar stepwise screening programmes in ADDITION-Denmark also showed that large-scale diabetes screening is feasible and acceptable [7]. However, it should be noted that few participants were diagnosed with diabetes, even in the high-risk groups identified in these programmes. In ADDITION-Cambridge, some groups were hard to reach, with lower uptake in deprived areas and among males and the obese, and attendance at the first screening stage did not ensure completion of the programme[5]. Similarly, in ADDITION-Netherlands, high-risk individuals were more likely to drop out of the programme [8] suggesting that different strategies may be required to increase uptake among high-risk individuals to ensure that health inequalities are not widened. Further research should inform decisions concerning whom to screen and in what setting in order to maximise uptake, particularly among those with most to gain. Approaches specific to different contexts and involving a range of providers may be appropriate, for example chemists and supermarkets. Research about optimal screening intervals is also required; shorter intervals will increase costs and false positive results, while longer intervals will increase population exposure to untreated hyperglycaemia.

"The benefit from the screening programme should outweigh the physical and psychological harm (caused by the test, diagnostic procedures and treatment)".

Potential harms, both direct and indirect, should be considered before implementing a large-scale screening programme. A small harm to the majority who test negative could outweigh a large benefit to the minority whose diabetes is detected by screening. Much relevant data, from observational studies and controlled trials, have been reported since 2001. Almost all studies suggest that screening for type 2 diabetes in the general population is associated with limited psychological adverse effects. In a controlled trial of the psychological impact of stepwise screening for diabetes among 7,380 participants in the ADDITION-Cambridge trial, anxiety, depression, worry about diabetes and self-rated health were not significantly different in participants invited to screening and those not invited (controls) shortly after screening and 3–6 and 12–15 months later [9]. A parallel cohort study in the same trial showed no differences between controls and those who screened negative for perceived personal risk, behavioural intentions or self-rated health, over the same time period suggesting that a negative test result does not promote false reassurance [10].

"The opportunity cost of the screening programme (including testing, diagnosis and treatment, administration, training and quality assurance) should be economically balanced in relation to expenditure on medical care as a whole (ie. value for money)".

Modelling studies have suggested that a programme of screening for diabetes every 4–5 years would be associated with a reduction in diabetes-related mortality of the order of 26–40% [11][12]. Kahn et al assessed the cost-effectiveness of eight simulated screening strategies compared to a no-screening control strategy using the Archimedes model [1]. Compared with no screening, all simulated screening strategies reduced the incidence of myocardial infarction and diabetes-related microvascular complications and increased the number of QALYs added over 50 years. Gillies et al modelled four different strategies for the screening and prevention of type 2 diabetes in the UK context: screening for diabetes; screening for diabetes and IGT, followed by either lifestyle intervention or drugs; and no screening [13]. The authors showed that it was likely to be cost-effective to intervene in those found to have impaired glucose regulation rather than wait for individuals to be diagnosed with diabetes. Although encouraging, modelling studies are only as robust as their underlying assumptions, and cannot substitute data from long-term RCTs. Uncertainties exist about key model parameters, as well as the real costs and benefits of screening, and practical considerations about the feasibility, acceptability and affordability of interventions. If screening for diabetes is to be undertaken, it should be as part of a wider strategy to prevent both diabetes and CVD and include assessment of CVD risk factors other than just glucose.

“All other options for managing the condition should have been considered (eg. improving treatment, providing other services), to ensure that no more cost effective intervention could be introduced or current interventions increased within the resources available.”

While much progress has been made in improving treatment for those with diabetes in the developed world, suboptimal care persists [14]. There are remaining gaps in treatment and the new therapies, improved education and management strategies are needed. Given that an effective screening programme will increase the demand for diabetes care, further work may be needed to optimise clinical care before introducing a national screening programme. Furthermore, in some countries, there are an overwhelming number of people with poorly treated diabetes [15]. Primary and tertiary prevention strategies may be a more appropriate use of scarce health resources than screening in these settings.

“There should be a plan for managing and monitoring the screening programme and an agreed set of quality assurance standards.”

Evidence from a national pilot screening programme for type 2 diabetes in deprived areas of England showed the difficulty in implementing and evaluating diabetes screening initiatives in primary care [16]. There was inconsistency in executing the screening protocol, lack of quality control, lack of adequate diagnostic testing after a positive screening test, and a lack of systems for routine data collection on screening. Furthermore, screening for a disease inevitably finds more people at high risk than people with the disease and it remains unclear what to do with these individuals in a real-world setting.

Results from the DEPLAN project, which aims to develop and test models of identification and intervention in individuals at high risk of type 2 diabetes in 17 European countries, will provide further evidence on effective ways of finding and treating those at risk of diabetes [17]. Similarly, the UK NHS “Health Checks” programme [18]will identify large numbers of people in primary care who might benefit from interventions to reduce their risk of CVD and diabetes and may provide opportunities to implement and evaluate different screening strategies.

“Adequate staffing and facilities for testing, diagnosis, treatment and programme management should be available prior to the commencement of the screening programme.”

The availability of staff and facilities remains uncertain in resource-constrained services, but screening could be undertaken by a range of providers in a range of settings. Whether there are adequate staff and facilities to support the implementation of a screening programme remains a context-specific decision since the cost-benefit ratio of diabetes screening may vary from one setting to another.

"Evidence-based information, explaining the consequences of testing, investigation and treatment, should be made available to potential participants to assist them in making an informed choice".

The DICISION trial examined the impact of an informed choice invitation compared to a standard invitation on uptake of diabetes screening in primary care [19]. An ‘informed choice’ invitation did not reduce overall attendance or affect attendance differentially by social class. These findings suggest that there is no reason not to provide full information on the pros and cons of diabetes screening, especially in view of recent scepticism about the net benefits of established mammographic screening programmes for breast cancer.

“Public pressure for widening the eligibility criteria, for reducing the screening interval, and for increasing the sensitivity of the testing process, should be anticipated. Decisions about these parameters should be scientifically justifiable to the public.”

There is little current evidence to inform this criterion.

References

  1. ^ Kahn, R., et al., Age at initiation and frequency of screening to detect type 2 diabetes: a cost-effectiveness analysis. Lancet, 2010. 375(9723): p. 1365-74.

  2. ^ Simmons, R.K., et al., Screening for type 2 diabetes and population mortality over 10 years (ADDITION-Cambridge): a cluster-randomised controlled trial. Lancet, 2012. 380(9855): p. 1741-8.

  3. ^ Echouffo-Tcheugui, J.B., Simmons, R.K., Prevost, A.T., Williams, K.M., Kinmonth, A-L., Wareham, N.J., Griffin, S.J., Impact of population-based stepwise screening for diabetes on cardiovascular morbidity, self-rated health and health behaviour: seven year follow-up of the ADDITION-Cambridge randomised controlled trial. In submission,, 2013.

  4. ^ Griffin, S.J., et al., Effect of early intensive multifactorial therapy on 5-year cardiovascular outcomes in individuals with type 2 diabetes detected by screening (ADDITION-Europe): a cluster-randomised trial. Lancet, 2011. 378(9786): p. 156-67.

  5. ^ Sargeant, L.A., et al., Who attends a UK diabetes screening programme? Findings from the ADDITION-Cambridge study. Diabet Med, 2010. 27(9): p. 995-1003.

  6. ^ Graffy, J., et al., More than measurement: practice team experiences of screening for type 2 diabetes. Fam Pract, 2010. 27(4): p. 386-94.

  7. ^ Dalsgaard, E.M., et al., Comparison of different stepwise screening strategies for type 2 diabetes: Finding from Danish general practice, Addition-DK. Prim Care Diabetes. 4(4): p. 223-9.

  8. ^ Janssen, P.G., et al., Low yield of population-based screening for Type 2 diabetes in the Netherlands: the ADDITION Netherlands study. Fam Pract, 2007. 24(6): p. 555-61.

  9. ^ Eborall, H.C., et al., Psychological impact of screening for type 2 diabetes: controlled trial and comparative study embedded in the ADDITION (Cambridge) randomised controlled trial. Bmj, 2007. 335(7618): p. 486.

  10. ^ Paddison, C.A., et al., Are people with negative diabetes screening tests falsely reassured? Parallel group cohort study embedded in the ADDITION (Cambridge) randomised controlled trial. Bmj, 2009. 339: p. b4535.

  11. ^ Chang, H.J., et al., Evaluation of a population-based screening for type 2 diabetes: a community-based screening project in Puli, Taiwan. Prev Med, 2000. 31(4): p. 396-402.

  12. ^ Kuo, H.S., et al., A Markov chain model to assess the efficacy of screening for non-insulin dependent diabetes mellitus (NIDDM). Int J Epidemiol, 1999. 28(2): p. 233-40.

  13. ^ Gillies, C.L., et al., Different strategies for screening and prevention of type 2 diabetes in adults: cost effectiveness analysis. Bmj, 2008. 336(7654): p. 1180-5.

  14. ^ Calvert, M., et al., Effect of the quality and outcomes framework on diabetes care in the United Kingdom: retrospective cohort study. Bmj, 2009. 338: p. b1870.

  15. ^ Home, P., The challenge of poorly controlled diabetes mellitus. Diabetes Metab, 2003. 29(2 Pt 1): p. 101-9.

  16. ^ Goyder, E., et al., Evaluating the impact of a national pilot screening programme for type 2 diabetes in deprived areas of England. Fam Pract, 2008. 25(5): p. 370-5.

  17. ^ Schwarz, P.E., et al., The European perspective of type 2 diabetes prevention: diabetes in Europe--prevention using lifestyle, physical activity and nutritional intervention (DE-PLAN) project. Exp Clin Endocrinol Diabetes, 2008. 116(3): p. 167-72.

  18. ^ Department of Health, Putting Prevention First. Vascular checks: risk assessment and management, Department of Health, Editor 2008: London.

  19. ^ Mann, E., et al., Impact of an informed choice invitation on uptake of screening for diabetes in primary care (DICISION): trial protocol. BMC Public Health, 2009. 9: p. 63.

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