BMJ  2003;327:E38-E39 (4 October), doi:10.1136/bmjusa.01060002 (published 5 September 2002)

BMJ USA: Editorial

The case for screening for type 2 diabetes in selected populations

We should follow the American Diabetes Association guidelines on screening

This article originally appeared in BMJ USA

Seven criteria should be considered when screening for a disease in an asymptomatic population.¹ These are: a) the disease represents an important health problem that imposes a significant burden on the population; b) the natural history of the disease is understood; c) there is a recognizable preclinical (asymptomatic) stage during which the disease can be diagnosed; d) tests are available that can detect the preclinical stage of the disease and the tests are acceptable and reliable; e) treatment after early detection yields benefits superior to those obtained when treatment is delayed; f) the costs of case finding and treatment are reasonable and are balanced in relation to health expenditures as a whole, and facilities and resources are available to treat newly diagnosed cases; and g) screening will be a systematic ongoing process and not merely an isolated one-time effort.

Selected populations recommended for screening for type 2 diabetes* 1.  Individuals 45 years (if normal, repeat at 3-year intervals) 2.  Testing should be considered at a younger age or be carried out more frequently in individuals who: are obese (120% desirable body weight or a BMI 27 kg/m2), have a first-degree relative with diabetes, are members of a high-risk ethnic population (eg, African American, Hispanic American, Native American, Asian American, Pacific Islander), have delivered a baby weighing >9 lbs or have been diagnosed with GDM, are hypertensive (140/90 mm Hg), have an HDL cholesterol level 35 mg/dl and/or a triglyceride level 250 mg/dl on previous testing, had IGT or IFG BMI = body mass index; GDM = gestational diabetes mellitus; HDL = high density lipoprotein; IGT = impaired glucose tolerance; IFG = impaired fasting glucose *Adapted from: American Diabetes Association. Screening for diabetes. Diabetes Care 2001;24(Suppl 1):S21-S24.

For type 2 diabetes, the case for the first three conditions is well established. The fourth condition is also met if one avoids (for the purpose of validating screening per se) the controversy of what specific values should be adopted. I would argue that the fifth condition is also met for the following reasons. The microvascular complications of diabetes are related to the duration of disease and the level of glycemia during that period. Randomized clinical trials have demonstrated that lowering glycemia decreased the development and progression of these microvascular complications. ^2-4 Since up to 25% of type 2 patients already have retinopathy when diagnosed,⁵ it seems obvious that if they had received effective treatment earlier, this complication would have at least been delayed, and possibly prevented.

The sixth condition is harder to evaluate. In general, population-based and selective community screening consume larger resources and are much less likely to have a long-term positive effect on health than opportunistic screening (i.e., screening when the individual interacts with the health care system). The cost-effectiveness of the latter, however, is comparable to screening programs recommended for some other diseases.¹ If the screened individual has an ongoing relationship with a health care provider, the last condition may well be met. If not, it probably won't be.

In a paper in this issue of BMJ USA (page 309), Wareham and Griffin agree with much of the above but conclude that universal screening for type 2 diabetes is not warranted.⁶ They do allow that screening in specific subgroups may be justified. I would certainly agree. The high-risk populations recommended for screening by the American Diabetes Association are listed in the box. Wareham and Griffin further stipulate that clinical management of type 2 diabetes should be "optimized" before a screening program is considered. This is very short sighted. The asymptomatic condition of type 2 diabetes often gets short shrift from today's hurried (some would say harried) physicians. In spite of that, diabetes care is improving. Witness the decline of 1.3 percentage points in average HbA1c levels in the United States, from 9.5% in the first part of the 1990s⁷ to 8.2% in the western part of the country in the latter half of the decade.⁸

One final point is that the increased risk for cardiovascular disease (CVD) extends down into the normal glycemic range. For instance, the four-year incidence of age-adjusted CVD in men between the ages of 45 to 79 years was increased 2.7-fold in those with HbA1c levels between 5.0% and 5.4% compared with those with values less than 5.0%.⁹ Furthermore, lowering glycemia in diabetic patients does not favorably affect cardiovascular outcomes.¹⁰ Therefore, using CVD as a justification for specific diagnostic criteria for diabetes, or even as an argument for diabetes screening, is not warranted in my view. We need to identify and address risk factors for CVD (which are present long before diabetes is diagnosed^{11 12}) independent of glycemic concerns.

In conclusion, screening for type 2 diabetes in selected populations (see box above) is important. In the long run, we will not only improve the lives of many people, but even save some scarce health resources.

http://bmj.com/cgi/content/full/322/7292/986

Charles R. Drew University, 1731 East 120th St., Los Angeles, CA 90059, USA (madavids{at}cdrewu.edu)

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Education and debate BMJ USA p 309

References

1. Engelgau MM, Venkat Narayan KM, Herman WH. Screening for type 2 diabetes (Technical Review). Diabetes Care 2000;23:1563-1580 (correction, Diabetes Care 2000;23:1868).[Abstract]
2. DCCT Research Group. The effect of intensive diabetes treatment on the development and progression of long-term complications in insulin-dependent diabetes mellitus. N Engl J Med 1993;329:977-986 [Abstract/Free Full Text]
3. Ohkubo Y, Kishikawa H, Araki E, et al. Intensive insulin therapy prevents the progression of diabetic microvascular complications in Japanese patients with non-insulin-dependent diabetes mellitus: a randomized prospective 6-year study. Diabetes Res & Clin Pract 1995;28:103-117 [CrossRef][ISI][Medline]
4. UK Prospective Diabetes Study (UKPDS) Group. Intensive blood-glucose control with sulphonylureas or insulin compared with conventional treatment and risk of complications in patients with type 2 diabetes (UKPDS 33). Lancet 1998;352:837-853 [CrossRef][ISI][Medline]
5. Harris MI. Undiagnosed NIDDM: clinical and public health issues. Diabetes Care 1993;16:642-652 [ISI][Medline]
6. Wareham NJ, Griffin SJ. Should we screen for type 2 diabetes? Evaluation against National Screening Committee criteria. BMJ 2001;322:986-988 [Free Full Text]
7. Davidson MB. Diabetes care in health maintenance organisation and fee-for-service settings. Dis Manage Health Outcomes 1997;2:189-197
8. Peters AL, Thompson R, Ryan D. Glycohemoglobin assessment program (GAP): what is the level of diabetes management in primary care? Diabetes 1999;48(Suppl 1):A194
9. Khaw K-T, Wareham N, Luben R, et al. Glycated haemoglobin, diabetes, and mortality in men in Norfolk cohort of European Prospective Investigation of Cancer and Nutrition (EPIC-Norfolk). BMJ 2001;322:15-18 [Abstract/Free Full Text]
10. Wild SH, Dunn CJ, McKeigue PM, Comte S. Glycemic control and cardiovascular disease in type 2 diabetes: a review. Diabetes Metab Res Rev 1999;15:197-204 [CrossRef][ISI][Medline]
11. McPhillips JB, Barrett-Connor E, Wingard D. Cardiovascular disease risk factors prior to the diagnosis of impaired glucose tolerance and non-insulin-dependent diabetes mellitus in a community of older adults. Am J Epidemiol 1990;131:443-453 [Abstract/Free Full Text]
12. Haffner SM, Stern MP, Hazuda HP, et al. Cardiovascular risk factors in confirmed prediabetic individuals: does the clock for coronary heart disease start ticking before the onset of clinical diabetes? JAMA 1990;263:2893-2898 [Abstract]

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