Screening for diabetesBMJ 2007; 335 doi: https://doi.org/10.1136/bmj.39323.395336.BE (Published 06 September 2007) Cite this as: BMJ 2007;335:457
- Ronald P Stolk, professor of clinical epidemiology
- Department of Epidemiology, University Medical Centre Groningen, University of Groningen, PO Box 30.001, 9700 RB Groningen, Netherlands
In this week's BMJ, two studies by Eborall and colleagues assess the psychological impact of screening for diabetes mellitus in primary care.1 2 Screening for diabetes is primarily aimed at preventing cardiovascular disease. The risk of cardiovascular disease increases proportionally as concentrations of glucose increase, with no threshold below which the risk remains constant.3 This is in contrast with other complications of diabetes—such as retinopathy, neuropathy, and nephropathy—the risk of which sharply increases when glucose concentrations exceed the threshold of 11 mmol/l. At this concentration the typical diagnostic signs of diabetes are usually present—thirst, polyuria, and weight loss.
Population based mass screening for diabetes has been proposed for several years.4 This has been fuelled by rising plasma glucose concentrations in most populations worldwide, as a result of increasing body weight associated with a more sedentary lifestyle and changes in diet. Arguments for mass screening include the fact that mildly increased plasma glucose does not cause symptoms and usually persists for several years, it can be determined by a capillary drop of blood, and it is associated with increased risk of cardiovascular disease.5
However, two questions need to be resolved before screening can be recommended. Firstly, will treating asymptomatic hyperglycaemia help prevent cardiovascular disease? Secondly, what psychological harm could be caused by anxiety regarding the screening result or the effects of a diagnosis that requires changes in diet and activity patterns and lifelong use of drugs?6 The first question should be answered by the ongoing international ADDITION trial into the effectiveness of multifactorial treatment for cardiovascular disease in people with screen detected diabetes.7
The two studies in this week's issue look at the second question, at least in white British people. Eborall and colleagues studied the psychological effects of stepwise screening programme for diabetes conducted within the Cambridge arm of the ADDITION trial. They found no changes in anxiety, depression, or worries about diabetes between the invitation for the first screening visit and a year after completing the programme.1 Moreover, the results did not differ significantly between people invited for screening and those who were not invited.
The authors also conducted a smaller qualitative study within the Cambridge ADDITION study at several time points during the stepwise screening process.2 Participants seemed to adapt their feelings about the possibility of having a chronic disease with each step in the screening process, thereby controlling the psychological burden.2 Both studies were hampered by a low response rate, which is probably not random. If people who were anxious about examinations, forms, and medical or research staff preferentially chose not to participate, a psychological harm of screening would be masked by selection bias. However, this is unlikely because the results are in line with the absence of psychological effects of blood pressure screening8 and with a smaller study in the Dutch part of the ADDITION trial.9
It is important to realise that the ADDITION study consisted of a stepwise screening procedure. Only people with an increased risk of diabetes—on the basis of a raised cardiovascular risk known to their general practitioner—were invited for the first examination. They had probably been counselled about their weight or were aware of their increased risk of cardiovascular disease because they had been prescribed drugs to lower their blood pressure. As Eborall and colleagues suggest,2 this might explain the limited psychological stress of the screening procedure and a diagnosis of diabetes—people were already aware of their high risk before the invitation for screening. Harmful psychological effects are more likely to occur in population based mass screening, where everybody within a certain age range is invited for a plasma glucose measurement (like breast cancer screening). In that situation, the stepwise approach is replaced by one large leap from feeling completely healthy to harsh lifestyle changes and lifelong use of drugs.
Targeted screening for diabetes, also referred to as case finding or opportunistic screening, means that health professionals measure glucose in people with a presumed increased risk of diabetes. Eborall and colleagues' results further tip the balance in favour of individual targeted screening over mass population screening for diabetes. Screening and diagnosis within the healthcare setting enables individually tailored follow-up and treatment.
Nevertheless, even though targeted screening may not increase psychological stress we still need to show that treating asymptomatic people with slightly raised glucose concentrations is effective. At the moment there is insufficient evidence to recommend screening for diabetes, and until the results of the ADDITION trial are known we will have to wait until people present with the classic symptoms of thirst and polyuria before testing them.
This article was posted on bmj.com on 31 August 2007: http://bmj.com/cgi/doi/10.1136/bmj.39323.395336.BE
Competing interests: None declared.
Provenance and peer review: Commissioned; not externally peer reviewed.