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Lipid Status and Screening for Type 2 Diabetes
Submit responseOur response to the reader’s comments follow. In making its recommendation on Screening for Type 2 Diabetes, the USPSTF considered interventions, including, lipid lowering agents, for effects on health outcomes such as cardiovascular events. In reviewing the evidence on lipid lowering agents, the USPSTF found that persons with diabetes do not appear to benefit to a greater extent than persons without diabetes for the primary prevention of cardiovascular events, whether considering absolute or relative risk reduction. For example, in the Heart Protection Study (HPS) to which the author refers, the absolute reduction in cardiovascular events for subjects receiving simvistatin versus placebo was similar in those with and without diabetes, 3.2% and 3.0% respectively (calculated from data in HPS) (1). Therefore, the evidence does not support screening for type 2 diabetes on the basis of lipid status. However, the USPSTF encourages clinicians to perform a global cardiovascular disease risk assessment to determine a person’s 10-year CVD risk (using tools such as the tool based on Framingham data, available at http://www.intmed.mcw.edu/clincalc/heartrisk.html), and to screen for type 2 diabetes if knowledge of diabetes status would change management, including the management of hypertension or the use of lipid lowering agents and aspirin. Thank you for this opportunity to respond to these comments. Conflict of Interest:None declared
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Criteria for screening for type 2 diabetes vs. criteria for screening for obesity
Submit responseThe U.S. Preventive Services Task Force (USPSTF) recently updated clinical guidelines on screening for type 2 diabetes mellitus in adults (1) and recommended against screening for type 2 diabetes, unless the patient had sustained blood pressure greater than 135/80 mm Hg. The updated guidelines also recommend against screening for impaired glucose tolerance (IGT) or impaired fasting glucose (IFG), which can be detected during screening for diabetes.
The USPSTF arrived at their conclusion because they could find no evidence that screening for type 2 diabetes, IGT or IFG resulted in improvement in “health outcomes” including cardiovascular morbidity, symptomatic neuropathy, nonhealing ulcers, lower-limb amputation, chronic kidney disease, severe visual impairment, mortality, or quality of life (1, p. 848).
In 2003 the USPSTF updated its clinical guidelines on screening for obesity in adults (2), and recommended that clinicians screen all adult patients for obesity and offer intensive counseling and behavioral interventions to promote sustained weight loss (2, p. 930). This recommendation was made without any caveats regarding blood pressure or any other physiologic risk factors.
It is noteworthy that the obesity screening recommendation was based on different criteria than those used to evaluate screening for pre- diabetes and type 2 diabetes. In fact the USPSTF found no evidence that behavioral interventions lower mortality or morbidity from obesity. Rather, the recommendation was based on the impact of modest weight loss on improvements in “intermediate outcomes” including glucose metabolism, lipid levels, and blood pressure (2, p. 930).
Ironically, in order to support their obesity screening recommendation, the USPSTF cited two clinical trials (3, p. 935; references 67, 81) showing that modest weight loss in persons with IGT resulted in dramatic reductions in the incidence of type 2 diabetes. These same trials have demonstrated that modest weight loss in persons with IGT also leads to significant improvement in multiple intermediate outcomes including blood glucose, blood pressure, lipids and triglyceride levels (4, 5).
Isn’t it fair to ask why the USPSTF uses such divergent criteria to rationalize screening for one chronic disease risk factor (i.e., obesity) but not the other (i.e., diabetes, IGT, IFG)?
References:
1. U.S. Preventive Services Task Force. Screening for type 2 diabetes mellitus in adults: U.S. Preventive Services Task Force Recommendation Statement. Ann Intern Med. 2008;148:846-854.
2. U.S. Preventive Services Task Force. Screening for obesity in adults: Recommendations and rationale. Ann Intern Med. 2003;139:930-949.
3. McTigue KM, Harris R, Hemphill B, Lux L, Sutton, S, Bunton AJ, Lohr KN. Screening and Interventions for Obesity in Adults: Summary of the Evidence for the U.S. Preventive Services Task Force. Ann Intern Med. 2003;139:933-949.
4. Tuomilehto J, Lindstrom J, Erikkson JG et al. Prevention of Type 2 Diabetes Mellitus by Changes in Lifestyle among Subjects with Impaired Glucose Tolerance. N Engl J Med 2001;344:1343-50.
5. Orchard TJ, Temprosa M, Goldberg R, et al. The Effect of Metformin and Intensive Lifestyle Intervention on the Metabolic Syndrome: The Diabetes Prevention Program Randomized Trial. Ann Intern Med. 2005;142:611 -619.
Conflict of Interest:
None declared
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USPSTF Recommendation About Screening For Type 2 Diabetes Mellitus In Adults With Hyperlipidemia
Submit responseThe USPSTF no longer recommends routine screening for type 2 diabetes mellitus (DM-2) in adults with hyperlipidemia (1). This recommendation appears to have been based, at least in part, on an analysis of the secondary prevention trials showing that lipid treatment reduced the incidence of CHD events by about the same relative percentage among those with DM-2 and those without.
Since the incidence of major CHD events is higher in adults with DM-2 than in those without, one would expect that diabetic patients would benefit more than nondiabetic patients despite similar reductions in relative percentage. Therefore, reductions in absolute percentage (and not relative percentage) of CHD events with lipid treatment in these groups should have been considered.
Reference: 1. USPSTF: Screening for Type 2 Diabetes mellitus in Adults: U.S. Preventive Service Task Force Recommendation Statement. Ann Intern Med. 2008;148:846-854
Conflict of Interest:
None declared